This PDF file contains the front matter associated with SPIE Proceedings Volume 11028, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Semiconductor nanowires, especially Si nanowires (SiNWs) have attracted much attention due to its high broadband absorption, high density and extra ordinary surface/volume ratio. Moreover, nanowires are ideal candidates for light detection, large responsivity, a fast response speed, and an excellent detection limit. These opto-physical properties demonstrates their high potential for practical applications in advanced devices such as transistors, photodetectors, lightemitting- diodes, solar cells, bio/chemical sensors, and etc. Graphene on the other hand, exhibits an extremely high charge carrier mobility, a very broad spectral range of detection from ultraviolet to terahertz and quasi wavelength independent absorption, which is a result of its gapless band nature. Compatibility of Graphene with Si or SiNWs makes it a promising candidate for large-scale and cost effective ultrafast photodetection. The growth of high-quality CVD graphene from camphor and its high performance optical device has not been addressed so far. We have presented high performance near infrared photodetectors (NIRPDs) by using camphor as solid source of carbon for developing mono-bi layer Gr/SiNW arrays schottky heterojunction. The nanowire arrays shows excellent optical light trapping properties and on the other hand, graphene act as transparent conductive metal sheet. Hence a combination of graphene over SiNWs serves as an excellent NIR light coupling system. The as-prepared device has also shown remarkable responsivity from μA/W to mA/W at 0 V bias, for Gr/Si and Gr/SiNWs heterojunction, respectively. On the other hand, as prepared device shows excellent responsivity up to 2V bias, which suggests that our approach to make graphene sheet by natural camphor will have a potential application to make self-driven low bias NIRPDs in future optoelectronic devices.

One design of state of the art laser scanner systems in automotive applications is based on oscillating mirror modules. The requirement of a large mirror surface for eye-safe transmission beams is a major drawback for fast and reproducible scanning. Tolerances of angular positioning, position sensing as well as vibrational perturbations limit the position accuracy of such a mirror and thus, the accuracy of the transmission spot position in the field of view (FoV). In contrast to scanner modules, Flash LiDAR systems provide high accuracy of spot positions. However, due to simultaneous illumination of the entire FoV, the maximum measurable range degrades. Our approach for a scanner module, presented in this paper, combines a micro lens array (MLA) with an objective lens for generating one optical telescope assembly for each angular scan position exclusively. The consequence is a maximum transmission beam diameter without angular FoV reduction along with minimum mirror dimensions. In order to avoid shadings between adjacent scan spots in the target distance, created by beam cut-offs at the aperture-stop of the objective lens, an array of optimized optical elements is provided additionally to the MLA. With adequate design of the MLA, the reliability of the scanner module regarding the angular positioning accuracy increases significantly. We demonstrate that the noise of the spot position is suppressed in dependence on the aperture-stop dimensions of the MLA. In conclusion, we present a new solution for a 3D LiDAR scanner module with a reliable spot-position accuracy comparable to 3D-camera/Flash LiDAR systems but with higher distance measurement range.

Choppers are widely used in optical sensing, including for radiometry and photometry, spectrometry, biomedical applications, and telescopes. While classical choppers are built with rotational disk, we have introduced and patented a novel device, with rotational shafts, which has the capability to surpass the maximum limit of around 10 kHz chopping frequency that characterizes choppers with disks. The main issue of such choppers with shafts comes from the high rotational speeds they can employ. This is an advantage in terms of the high chopping frequency they can produce, but it imposes the necessity to perform a Finite Element Analysis (FEA) of the fast rotational shafts. While in previous studies we approached cylindrical shafts for the chopper, in the present one we consider spherical shafts. Optical aspects of such devices – regarding the transmission functions produced – have been presented in previous studies. In the present one we focus on the FEA of these choppers. Different dimensions and a range of rotational speeds of up to 60 krpm are considered. The main working conditions that are imposed are the structural integrity and the acceptable level of (elastic) deformations of the chopper shafts. Limits of the rotational speed at which the choppers can (still) work are discussed from these two points of view – with regard to the characteristics of the device.

Fiber Bragg Gratings (FBGs) have been used and deployed in several applications and industries over the past years. Standard FBG based temperature sensors are sensitive to both strain and temperature and in order to measure temperature, the strain influence needs to be isolated from the FBG by careful transducer design, packaging and calibration of the sensor. Birefringent FBGs such as polarization maintaining FBGs (PM-FBG) that can simultaneously measure strain and temperature have been demonstrated in recent publications. Such sensors exhibit a double FBG response which is polarization dependent and the wavelength peak separation is an important parameter to enable measurements beyond standard FBGs. To achieve the best performance of a birefringent FBG, an optimized interrogation technique that can measure both FBG orthogonal polarization responses with high precision is required. In addition to the need for an optimized interrogator, the selection of sensor inscription method, coating type, mounting technique, and calibration are very important parameters to deliver the best overall system performance. PM-FBG sensors can be multiplexed on a single fiber and offer a simplified installation option without the requirement for complex transducer packaging designs. Here we have developed as part of an ESA GSTP project, a fiber optic sensing system for birefringent FBGs based on a high precision tunable laser interrogator system. We have also evaluated different types of PM-FBG sensors with different coatings and mounting techniques and demonstrated an optical temperature measurement system with an operating temperature range from -20°C to + 80°C using PM-FBGs with improved calibration techniques.

On-line measurement of fiber core-temperature is very important for the investigations of high-power fiber lasers. Using thermal infrared imager is currently the most common approach to detect the temperature of fiber, even though it only monitor the surface temperature. So the measurement result is greatly different from the actual temperature of fiber core. Fiber Bragg Gratings (FBGs) have been widely used in detecting many physical quantities, such as strain, temperature, compression strength and curvature due to its intrinsic advantages, including simple manufacture technology, low insertion loss. Here, a new method based on FBG for measuring the temperature of fiber core is presented and experimentally demonstrated. We use a mutiple inscription method that inscribe a low reflectivity FBG on the high reflectivity chirp grating location as a fiber core temperature on-line monitor. Due to the resonant wavelength of chirp grating (1080nm) is far away from FBG’s resonance peak (1550nm), it means that the presence of FBG will not impact the performance of the chirp grating. Alongside this composite optical fiber structure is applied to fiber oscillator we inject a amplified spontaneous emission (ASE) light with the wavelength range near 1550 nm from the signal fiber of (2+1)*1 combiner. And then, the reflection spectrum of FBG can be record from the port 2 of circulator. The temperature of chirp grating and low reflectivity FBG can be measure by recording the shift of FBG’s resonance peak after the lineal relation between resonance wavelength and temperature are cofirmed. In order to detect the accuracy of this new structure, we also use Optical Frequency Domain Reflectometer (OFDR) to measure the temperature of the chirp grating. Experiment results prove the high accuracy of proposed temperature monitor. It is strongly believed that the novel proposed structure can be used to achieve measurement of fiber core temperature in high-power fiber lasers. This work also provides a novel idea for manufacturing multi-functional composite fiber structure.

We compare four different sensing solutions suitable for distributed fiber optic humidity sensing in perfluorinated graded-index polymer optical fibers (PFGI-POFs). Compared to silica fibers, polymer optical fibers offer advantageous benefits including significantly higher break down strain, fracture toughness and humidity sensitivity. Various humidity-related effects in PFGI-POFs have been reported in the last years including measured attenuation and length changes as well as Brillouin frequency and Bragg wavelength shifts. The four aforementioned methods could serve as a basis for distributed and quasi-distributed humidity sensing and are described here closely with an emphasis on plausible cross effects to temperature and strain. The main focus of this paper lies on the comparison of four approaches with regard to method complexity, sensitivity to humidity, spatial resolution, real-time capability and effort to compensate for cross effects.

The response of an interferometric low-coherence fiber-optic electric current sensor (FOCS) to a short current pulse is studied theoretically and experimentally. The main feature of current pulse sensing is analyzed that manifests itself when the duration of the pulse is comparable to or less than the light propagation time in the sensing fiber. An advanced small-radius sensing fiber coil is considered that allows one to improve the characteristics of FOCSs. In addition, the effect of the intensity noise due to the beating of the spectral components of radiation on the FOCS is studied. It is experimentally shown that this intensity noise can be reduced by using a two-channel optical scheme.

In this work, we present a concept and method to fabricate miniature, high-quality optical fiber interferometers for sensing applications. The sensitive part of our devices consists of an off-center polymer micro-cap bonded on the end of a single mode fiber (SMF). The SMF end can be cleaved with a small angle or polished flat. In our devices, the reflection from the interface between the polymer and the external medium can be adjusted with an axial misalignment between the core of the SMF and the polymer micro-cap. This allows us to control the fringe contrast of the interference pattern. We fabricated several samples and they were tested as temperature, refractive index, and humidity sensors. In each case, our sensors were compared with commercial ones. Our results suggest that our devices are as accurate and sensitive as wellcalibrated electronic sensors. The sensitivities were found to be 270 pm/°C for temperature sensing and 0.04 RH% for humidity sensing. As refractometers, our interferometers have a resolution of 10^-4 over a broad measuring range that goes from 1 to 1.54. Some applications of the devices here proposed can be monitoring of temperature or humidity in small spaces and refractive index of liquids inside of micro-fluidic channels. An advantage of our sensors is their broad operating wavelength range (from 800 to 1600 nm, approximately). In addition, the thermo-optic or thermal-expansion coefficients of polymers can be tailored. This may allow, for example, to tailor the performance of our sensor depending on the parameter to be sensed.

Random matrices exhibit interesting statistical properties which are studied under random matrix theory (RMT). In this research study, we present a novel approach for fiber optic distributed acoustic vibration sensing (DAS) systems which is based on the recent results of RMT. Our focus is the phase-sensitive optical time domain reflectometry (φ−OTDR) systems and the evaluation of the RMT at the photo-detection output. Inspired by the successful application of RMT in diverse signal processing applications, the RMT based signal detection methodology is transferred to DAS domain. The classical spectral theorem is revisited with special emphasis on the covariance of the measured Rayleigh backscattered optical energy which is a Wishart type random matrix. A real φ−OTDR system is evaluated for experimental verification of the statistical distributions of the extreme eigenvalues of the optical covariance matrix. It is shown that even with limited measured data, after proper conditioning and scaling of the optical detector output, the empirical bulk eigenvalue distributions are in good agreement with the analytical proof for the infinite data assumption. It is experimentally verified that the extreme eigenvalues of the optical covariance are bounded by the Marchenko-Pastur theorem and any outlier can be considered as a vibration presence. Additionally, it is shown that the eigenvalue bounds can be used to detect and track the vibrations along a fiber optic cable route.

By measuring the shift in the resonant frequency of whispering gallery modes in an optical microcavity, it is possible to obtain very high sensitivity to changes in the properties of the surrounding medium and the sensor surface. However, a narrow linewidth tunable laser is typically required in order to track the frequency shift. This significantly increases the cost and complexity of such systems. Phase shift cavity ring down spectroscopy (PS- CRDS) represents an alternative approach. In PS-CRDS the interrogating optical signal is sinusoidally modulated and the shift in the phase of the detected signal (rather than the shift in the cavity resonant wavelength) provides information about changes in the cavity properties. PS-CRDS has previously been successfully implemented in resonant optical microcavities, but a tunable laser was still used in order to maintain coupling to the cavity resonance. Here we consider the use of a broadband optical source (e.g. a diode laser or LED) to interrogate the cavity using the PS-CRDS principle. The spectrum of the source always spans more than one cavity resonance and so does not need to be tuned as the cavity resonances shift. We undertake an analytical and experimental investigation to evaluate the effectiveness of this approach and compare it to traditional interrogation methods in terms of sensitivity and signal-to-noise ratio. We focus in particular on the implementation of a resonant cavity biosensor in silicon photonics ring resonators. The results of the study show that the sensitivity to changes in cavity mode loss is slightly lower than when a narrow linewidth source is used, and that sensitivity to changes in the effective refractive index is very significantly reduced. We will discuss the implications of these results in terms of suitable applications of this technique, and the improved potential for integration that the low coherence source brings.

Filtering strategies are a crucial aspect for signal detection in many fluorescence based systems such as chemical and/or biochemical sensors. The design, fabrication and characterization of a new waveguide absorption filter for the optimization of the fluorescence signal collection, thanks to its high numerical aperture, is here presented. The absorption filter is designed to work as an optical waveguide in order to increase the optical path and, consequently, the absorption of the excitation light. A comparison of the performances of the absorption filter and a conventional interference filter, with particular emphasis on the angular dependence of the spectral features, is also reported. We experimentally demonstrate, for what regards the attenuation capability of the excitation signal, the failure of the interference filter for incidence angles greater than 15° and the validity of the absorbing waveguide filter for large incidence angles. Finally, preliminary results performed in fluorescence on an IgG labelled/ anti-IgG assay show the improvement in detected fluorescence intensity collected by means of the proposed absorption filter compared to that measured with the interference filter. This suggests that the filtering strategy based on the waveguide absorption filter can greatly simplify fluorescence detection systems and find interesting applications in different areas of sensing, from Point of Care Testing (POCT) to environmental monitoring.

The localization of the electromagnetic field at the nanoscale can play a key role in many applications, such as sensing, spectroscopy and energy conversion. In the last years, great efforts have been performed to study and realize all-dielectric loss-free nanostructures to confine the radiation without the limits imposed by plasmonic systems. It has been demonstrated that an all-dielectric photonic crystal (PhC) metasurface can support bound states in the continuum (BICs) - resonant states of infinite lifetime - due to the interaction between trapped electromagnetic modes. Experimentally, this involves very narrow coupled resonances, with a high Q-factor and a possible extremely large field intensity enhancement, up to 6 orders of magnitude. Here, we demonstrate that the field enhancement in proximity of the surface can be explored to boost lightmatter interaction in spectroscopic sensing. We design and realize an innovative sensing scheme for bulk and surface measurement with ultra-high figure of merit for the recognition of protein-protein interaction and the detection of low molecular weight molecules. In addition, we design a dielectric dual scheme based on metasurfaces supporting BICs to amplify fluorescence emission and Raman scattering of probe molecules dispersed on the surface of the PhC. Our results provide new solutions for light manipulation at the nanoscale, especially for sensing and nonlinear optics applications.

Upon reflection from the interface of two media, the light beam experiences two optical shifts: a longitudinal shift in the plane of incidence and a transverse shift normal to the plane, often referred to as Goos-Hänchen (GH) shift and Imbert-Fedorov (IF) shift . Simultaneously, the reflected light beam also experiences a small in-plane and out-of-plane angular deviation from the prediction of Snell’s law, i.e., the angular GH and IF shift, respectively. GH and IF shifts have attracted much attention in recent years due to their potential applications in many aspects, such as optical waveguide switch, integrated optics, and optical sensors. The GH and IF shifts have been widely investigated in various media and optical structures, such as dielectric slabs, metal surfaces, photonic crystal, and metasurfaces. The temperature-dependent GH shift has been investigated theoretically and experimentally, and proposed to detect the temperature variations. However, to the best of our knowledge, only the spatial GH shift was included in the reported temperature sensors based on GH shift, whereas the angular GH effect was neglected. In addition, IF shift based temperature sensor has not been addressed yet. In this work, we theoretically investigate the temperature-dependent spatial and angular GH and IF shifts of reflected light beam from the interface of air/gold film, and demonstrate a temperature sensor based on the GH (IF) shift. The spatial GH shift for the s-polarized light with a wavelength of 633 nm is negative, while the p-polarized light exhibits a positive spatial GH shift with a significantly larger amplitude. The s-polarized light possesses a negative angular GH shift with its amplitude increases with the incident angle. For the p-polarized light, it exhibits positive and negative angular GH shifts, which depends on the incident angle. The s-polarized light exhibits a positive spatial IF shift. For the angular IF shift, it is negative for the s-polarized light, whereas the p-polarized light possesses a positive angular IF shift. The spatial and angular shift of the reflected beam can be combined into a total beam displacement when observed with a distance from the origin. For temperature sensing applications, the total beam displacement of the GH (IF) effect between the p- and s-polarized incident light was monitored. It is found that both the GH and IF shift based temperature sensor exhibit positive and negative sensitivities. The maximum sensitivity (amplitude) for the GH shift temperature sensor was obtained from 633 nm light beam incident onto the surface of gold film at almost grazing incidence (e.g., 0.3631 nm/K with the incident angle of 89 degrees). In contrast, a much smaller sensitivity of 0.01615 nm/K was obtained for temperature sensor based on the spatial GH shift. The maximum sensitivity is 0.09477 nm/K for the IF shift based temperature sensor, much smaller than that based on the GH shift. The sensitivity of the temperature sensor also depends on the wavelength of incident light. The maximum sensitivity for the GH shift temperature sensor increases with the wavelength, and the sensitivity of 6.337 nm/K was achieved using 3000 nm light at the almost grazing incidence. For the IF shift temperature sensor, the maximum sensitivity decreases with the wavelength of incident light. The findings will open up new opportunities for the development of GH and IF shift based highly sensitive optical thermometry.

Laser interferometry is one of the most useful measurement techniques due to its advantages of long measurement range, high measurement resolution, and flexible arrangement. Various kinds of laser interferometers are designed according to their application fields or corresponding objectives such as for measuring displacement, velocity, refractive index, wafer warpage, or geometry errors. According to the measurement principles, interferometers can be classified into two measurement types, wavelength-based and grating-based. The problem of poor measurement stability caused by the unstable wavelength of the light source is difficult to avoid. This problem might affect the accuracy of measurement results obtained from interferometer if compensation technique of unstable wavelength light source is not utilized. Grating-based laser interferometer, also known as laser encoder, is proposed to overcome the problem caused by the unstable wavelength due to the phase variation of grating-based interferometer is independent from the wavelength of the light source. Many studies based on the measurement principle of grating-based interferometer have been carried out to measure displacement precisely. Each method comes with its own merits and limitations. In this study, a grating-based interferometer based on recurring-diffraction technique is proposed for displacement measurement. This interferometer has the merits of grating interferometry, heterodyne interferometry, and recurring-diffraction optical configuration. It has the capability of measuring in-plane displacement with high resolution and stability. The proposed system takes advantage of a “recurring-diffraction” optical configuration, which directs diffracted light to pass through two gratings triple times without additional optical components, thereby enhancing the phase change induced by grating displacement, effectively improving the resolution of the grating-based interferometer. Both the feasibility and performance of the proposed grating-based interferometer have been addressed and demonstrated in several experiments. The experimental results show that our proposed interferometer is capable of measuring in-plane displacement with the resolution of 2 nm, and the repeatability better than 1 nm. The proposed grating-based interferometer has excellent measurement properties, and is well-suited for applications within precision manufacturing, tool machine industry, automatic optical measurement, nanotechnology, semi-conductor technology and other related fields. Compared with other measurement instructions, this interferometer has the advantages of high resolution, high stability, relatively straightforward operation, and high flexibility.

A random laser is an optical system where the light is amplified by stimulated emission along random paths in a disordered medium. In recent years, a new kind of non-invasive sensor based on random lasing has been proposed. The striking point is that a sensor based on random lasing has an emission "fed" by the feedback due to the scattering properties of the medium, making such a system a natural candidate for studying materials with strong disorder. Here, we report the recent advances in the sensor structure and performances.

Microresonators have drawn a great deal of interest for their importance in both practical applications and fundamental physics in light-matter interaction. The optical confinement provided by a microresonator greatly enhances the interaction between optical spatial mode and the light emitting materials. Conventional fabrication of microresonators adopting semiconductor processing technology (no matter top-down or bottom-up approach) still faces some challenges. Here we report the feasibility of constructing solid state microresonators with various configurations including spheres, hemispheres and fibers from organic polymer in a flexible way. We realize optically pumped lasing from these structures after incorporating organic dye materials and/or colloidal quantum dots into the resonators. The lasing characteristics have been systematically examined in terms of size dependence and polarization. The longitudinal optical modes are well defined by whispering gallery modes. We are also able to tune the resonance modes by deforming the shape of micro-spheres, representing the facile manipulation of light-matter interaction. Finally, refractive index sensing with high sensitivity can be readily realized from these structures enabled by the existence of evanescent waves and improved by Vernier effect in coupled resonators.

Metal-enhanced fluorescence (MEF) is that enhanced by a localized surface plasmon. In the conventional scheme of MEF the RhB or other fluorescent molecules attached by Van-der-Waals forces to a plasmonic nanoparticle (PNP) form an array in which each element interacts separately with the PNP since the emission under the optical pumping is spontaneous (if we do not consider the case when the spaser generation threshold is achieved). This interaction is as a rule described in terms of the Purcell effect – the molecule at the fluorescence frequency is an electric dipole with very small dipole moment, which, however, induces a large resonant electric dipole in the PNP if the coupling is sufficient for the power transfer. The increase of the dipole moment, or, equivalently the increase of the radiative resistance of the quantum emitter is described by the radiative Purcell factor (the total Purcell factor corresponds to the increase of the effective resistance of the emitter, including the dissipative resistance). This concept of the Purcell effect introduced into nanophotonics by E. Yablonovich, however, did not comprise an equivalent scheme suitable for corresponding calculations. Purcell’s factor was calculated via the Green function until 2015 when our paper [1] was published. In the same year, this circuit model was extended to beyond the case of the weak near-field coupling (Purcell effect) and it turned out to be adequate for the description of the Lamb shift of the spectral maximum, of the Fano resonance, of the Rabi splitting of the fluorescence spectrum, and, finally, of the fluorescence quenching [2]. In fact, there is no physical difference does the resonance of the classical scatterer to which the quantum emitter is coupled result from the localized surface plasmon or from the Mie resonance of a dielectric particle. Therefore, the phenomenon of metal-enhanced or plasmon-enhanced fluorescence should unite with the electric or magnetic Mie resonance. The last case makes sense for chiral molecules and magnetic transitions. Thus, the effective circuit models the general phenomenon I call the dipole-enhanced emission. Besides the enhanced fluorescence, this term covers also conventional (without collective effects) schemes of surface-enhanced Raman scattering (SERS). The fundamental difference of the Raman scattering from the fluorescence is the robustness of the molecular vibration to the dipole-dipole coupling that is not capable to reshape the spectrum of the Raman signal. In this meaning, the interaction of the emitter with the resonant dipole keeps weak. Thus, in the equivalent circuit of SERS the emission of a molecule models by an effective current generator, whereas in the fluorescence the emission ability is an effective negative resistor. In the present report, I concentrate on the case of the weak coupling (Purcell effect) and consider only MEF. My goal is to show that the circuit model keeps ultimately simple for a core-shell PNP. Calculation of the circuit parameters does not require full-wave numerical simulations or numerical solution of any equations. The model is validated by a comparison with the literature data. References: 1. A.E. Krasnok, A.P. Slobozhanyuk, C.R. Simovski, S.A. Tretyakov, A.N. Poddubny, A.E. Miroshnichenko, Y.S. Kivshar, and P.A. Belov, Scientific Reports, vol. 5, 12956, 2015 2. C. Simovski, Photonics, vol. 2, 568-593, 2015

The proposed application has been developed to detect CRP, salmonella, and amitriptyline (AMT) on the basis of a structured lateral flow chip. It is combined with a read-out system using the camera of a smartphone and software such as ImageJ or a specially programmed app to evaluate color depth proportional to concentration. These strips are structured for multi-channel applications for either multi-analyte or for replica measurements. Calibration curves are provided for analytes, structuring and read-out will be discussed. The results allow the application in the area of POCT (point-of-care diagnostics), Anywhere care, or citizen science.

The continually growing use of glyphosate and its critically discussed health and biodiversity risks demand for fast, low cost, on-site sensing technologies for food and water. To address this problem, we designed a highly sensitive sensor built on biomimetic principles. In particular, the remarkably specific recognition of glyphosate by its natural target 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase was adapted in a biosensing approach. A site-specific immobilization strategy based on self-assembling fungal surface protein chimera was applied to assure accurate orientation of the enzyme’s active center on a biochip surface. The low binding affinity of the EPSP synthase – glyphosate binary complex was tackled by the usage of soft colloidal probe (SCP) assay known to detect weak binding energies based on surface interaction and elastic probe deformation. SCPs composed of polyethylene glycol hydrogels with a typical diameter of 10 - 50 micrometers and a young’s modulus of 47 kPa were equipped with carboxylic acid moieties for further functionalization with diamine and amino acid linkers of different lengths to tune the coupling of inhibitor or competitor molecules, i.e. glyphosate. Based on enzyme-inhibitor interactions, exposure of the EPSP synthase decorated biochip to glyphosate containing samples causes formation of enzyme-analyte-complexes and therefore a competitive loss of available binding sites for glyphosate-coated SCPs. Consequently, analyte (glyphosate) concentration can be associated with a differential adhesion between SCP and biochip surface. The microscopically detectable changes in SCP-biochip interaction is read out by reflection interference contrast microscopy, which is both low-budget but highly sensitive in terms of contact areas of highly transparent, non-labeled SCPs. Supported by automated image analysis algorithms this concept proved exceptional sensitivity even in the fM range in aqueous analyte solutions as well as high specificity in comparison to structurally related compounds. Taken together, we introduce a new concept for highly precise and specific detection of the wide-spread used but critically discussed herbicide glyphosate using a low-budget and fast detection system.

Surface-enhanced Raman scattering (SERS) has been proven a powerful means in detecting molecules/chemicals at trace levels due to its huge enhancement in the signal intensity of the finger prints of the molecules. The SERS experiments were carried out using Ag nanorods deposited on silicon substrates homogeneously, by e-beam glancing angle deposition (GLAD) technique, with controlled morphology and size, guranteening the homogeneity of the SERS signals from area to area. However, these substrates are facing several problems due to the thermal stability, temporal stability and chemical stability, etc. of Ag nanostructures. We proposed several approaches to solve these problems to make Ag-based nanostructures applicable as SERS substrates. In addition, we proposed a method to quantify the composition of chemical mixtures at trace levels by SERS, based on the principle components analysis (PCA), which is a statistical method normally used to distinguish chemicals in mixtures. The method was evidenced to be effective in predicting the composition of binary, ternary mixtures and even mixtures consisting of more components at trace levels by SERS, with acceptable errors.

There has recently been an extensive amount of work in the field of nanoplasmonics, where plasmonic phenomena occurring on a variety of nanostructrues present an alternative approach to surface plasmon resonance (SPR) biosensing. The architectures of these nanostructures are often complex, where localized regions of high plasmonic activity (sensitive to RI changes) are interdispersed among regions of little to no plasmonic activity (with no RI sensitivity). To date, the bulk of work on nanoplasmonic sensors has focused on the optimization of a nanostructure in terms of its optical characteristics, in terms of either its sensitivity to RI changes or likewise, in its figure of merit (FOM). In contrast, there has been very little discussion on the role of analyte transport in nanoplasmonic sensing. It is known that the selective immobilization of bioreceptors only to the sensitive regions can lead to significant increases in sensing performance: a result that is solely tied to increases in analyte transport. Hence, when selectively functionalized and operated under diffusion-limited conditions, the rate of analyte transport becomes strongly dependent on the nanoplasmonic architecture. Using numerical results, we have previously shown that this rate is dependent on two factors (i) the fill fraction of the sensitive regions, and (ii) the difference in size between individual localized sensitive regions and the overall size of the sensing surface. Despite the lack of discussion, the role of analyte transport remains paramount for the design of a nanoplasmonic structure. For example, changes to a nanostructure that result in an increase in RI sensitivity might induce a decrease in the rate of analyte capture, resulting in a sensor with an overall reduction in performance. In this talk we will demonstrate the ties between optical performance and the rate of analyte transport. We will present experimental data taken from a variety of plasmonic nanostructures, including variation of both their base photonic element (nanorods, nanodisks, and wires) as well as their packing density. We will show that, despite the large differences in optical characteristics, the characteristics of analyte transport follow relatively simple scaling trends. We will show that these experimental data have very good match to analytical predictions. In addition, we will discuss how the kinetics between analyte and bioreceptor will affect the optimal design of a nanostructure: sparse arrays of photonic elements have dominant performance for systems having strong kinetics, whereas for systems with poor kinetics, dense arrays of photonic elements have better performance.

The analysis of surface water, groundwater, drinking water as well as sewage is important to get information about the contamination of the water cycle. Currently, these time-consuming investigations require special equipment, like for example hyphenated mass spectrometry. Surface plasmon resonance (SPR) is a faster alternative as it is highly sensitive to changes in the dielectric medium next to a thin metal layer and makes it a quasi-universal detector. Therefore, and due to the labelfree nature, SPR is a widely used sensing tool for real‐time monitoring of molecular interactions of various analytes. SPR imaging (SPRi) has several advantages to standard surface plasmon resonance, as it allows to observe many analytes in parallel as well as the integration of referencing technologies. However, the homogenous illumination of a large area (several millimeters) with a small light source is challenging and demands new approaches. Allopurinol, a drug used to lower the blood concentration of urate and hence decrease the affection of gout, gets metabolized to oxipurinol in the body and dropped out almost entirely by urinary excretion. After wastewater treatment, concentrations of oxipurinol up to 21.7 μg•L^-1 are detected. Further tracking of oxipurinol in the urban water cycle showed its presence in rivers and streams or even in groundwater. Therefore, the high biological stability of oxipurinol allows this molecule to be used as a marker for domestic wastewater in the environment. For the detection of oxipurinol by SPR graphene was used as receptive layer, as the analyte can bind via π-stacking to this surface. An SPRi technique was developed and compared to conventional SPR system for the detection of oxipurinol.

We report the results of analysis of ways of application of nanostructured metasurfaces in rotation angle sensor (angle encoders). The dependence of optical properties of nanostructured metasurfaces upon their orientation relative to the incident optical radiation service as the basis of the study. The metasurfaces’ response to the incident radiation allows to judged on the mutual orientation of the radiation source and the metasurface. This allows to use metasurfaces as angle encoder scales. We discuss the possibility of using of amplitude and phase response of different types of metasurfaces. The main attention is paid to metasurfaces in the form of plasmonic nanorods, Pancharatnam–Berry elements and Cshaped antennas. The overall dimensions of the scales of angular encoders based on metasurfaces (width and length or diameter) can be tens of microns or less. Thus, the use of metasurfaces in angular encoders allows to reduce their size by orders of magnitude. Alongside, the use of metasurfaces should allow to realize non-contact measurements of the rotation angle (when only the scale based on the metasurface is placed on the controlled object or a part of an object itself acts as a scale) and to implement an absolute rotation angle sensor without significant increase of its size and manufacture complexity.

In this work, we reconsider optical transillumination for in vivo tissue imaging and for detection of time-dependent vital signs. Two portable optoelectronic instrumental configurations have been assembled and tested to achieve efficient transillumination and image detection of the inner structure of diffusing non-homogeneous biological samples with thickness of a few centimeters, with a resolution sufficient for differentiating internal macroscopic tissue structures. Tissue illumination is obtained with an extended source consisting in a matrix of Near Infra-Red (NIR) light emitters. To demonstrate the potentiality of this system for generating low resolution images of in vivo human tissues, it has been employed for transilluminating human upper limbs. Images featuring good contrast are acquired non-invasively with a monochrome CMOS camera turned into a wavelength selective image detector using optical filters. The collected images of human hands provide a clear visualization of the hand dorsal vein pattern. From recorded videos, we extract a timevarying signal that closely resembles the blood pressure wave: in its spectral content we recognize the frequency components corresponding to the expected heart and breath rates.

Surface plasmon resonance (SPR) sensing technology is widely used in the field of biosensors due to its non-marking, high-sensitivity, and non-invasive characteristics. However, SPR technology is still limited to sensing analysis in twodimensional plane, axial detection, as the key of SPR application in three-dimensional medium spatial detection, has not been well studied and solved. In an angle-interrogation SPR sensing system, the spatial characteristics of evanescent wave-dielectric interaction at multiple wavelengths are studied, and the factors affecting the spatial distribution of surface plasmon resonance are also analyzed. An axial spatial resolution method based on the particle swarm optimization (PSO) algorithm with multi-wavelength angle-interrogation structure is proposed, the refractive index distribution in axial space is determined by analyzing the characteristic SPR signal. In addition, the calculation and analysis of the applicable range of wavelengths are carried out. In the reliable spectral range of the incident light wavelength of 600-900 nm, the average error of the axial refractive index spatial resolution increases from 10^-5 RIU to 10^-4 RIU as the number of axial layers increases. The proposed multi-wavelength angle modulation structure analysis method based on PSO algorithm extends the SPR detection range from two-dimensional plane to three-dimensional space, which provides a new and promising analysis model for molecular biology.

Aerosol optical thickness is a very important parameters in the atmospheric correction of the hyperspectral data. In this study, an improved dense dark vegetation (DDV) based algorithm is introduced to estimate the AOT@550nm from hyperspectral remote sensing data. A correction relationship between TOA and land surface reflectance at short wavelength near 2.13μm was introduced in order to reduce the assumption of the traditional DDV that the TOA reflectance is equal to the land surface reflectance at short wavelength near 2.13μm. Simulated hyperspectral data of Hyperion sensor were applied to the improved DDV algorithm. The retrieved AOT @550nm show a well correlation with the actual values and the correlation coefficients is larger than 0.99.

Background: A requisite for fNIRS studies of cortical blood flow is that sufficient photons are transmitted transcutaneously for the fluctuations in cerebral hemoglobin oxygenation that occur during neuronal activation to be detected. Transmission is determined by the specifications of the fNIRS device, but also influenced by the characteristics of the skin. Epidermal pigments can attenuate photon transmission; the literature states that in dark skinned subjects some NIRS devices may not achieve sufficient photon migration to monitor cortical blood flow. Hence, as fNIRS use is spreading, we describe a simple head tilt maneuver where positional redistribution of cerebral blood volume will confirm if photon transmission is sufficient. Methods: A repetitive head tilt maneuver (bending forward from a seated position, hold for 30 seconds, returning to original position X 5) performed by a pigmented (African) subject and a non-pigmented (Caucasian) subject. A 23- channel portable fNIRS system with dual wavelength (750 and 860 nm) emitters and photodiode detectors was worn over the anterior cortex, and changes in oxy, deoxy and total hemoglobin concentration measured at 50 Hz. Results: Data from both subjects were compared and found to have a comparable pattern of change in oxyhemoglobin concentration and temporal response to the effects of head tilt; clear arterial pulsations and minimal noise were also evident. Conclusion: We suggest the head tilt maneuver described as a feasible test to confirm the adequacy of transcutaneous photon transmission where fNIRS studies are to be performed in subjects with pigmented skin to detect hemodynamic change in the cortex.

Various heating processes are used in a steel works. However, emissivity compensation is still one of the most difficult problems when radiation thermometers are applied to temperature measurements of heated sheets in steel manufacturing processes. The authors propose a new technique using spectral information of radiation from targets and multivariate analysis, such as principal component analysis (PCA) or partial least squares (PLS) analysis, etc. First, spectral radiation from a target is measured by a hyperspectral camera, and the scores of a predetermined spectral component are calculated as inner products of the measured spectral radiation and the predetermined spectral component. Second, the spectral component is predetermined so that its scores change with temperature and are minimally affected by the deviation of spectral emissivity. For example, the component can be determined by PCA under the condition that it is perpendicular to the deviation of spectral emissivity, which is evaluated in advance. Finally, temperatures are calculated from the scores and a calibration curve relating the scores to temperatures. The calibration curve is determined in advance from the measured spectral radiations from a blackbody furnace and the scores of the component at several temperatures. The authors developed a radiation thermometer using a hyperspectral camera and installed the camera at an annealing furnace in the stainless steel manufacturing process. As a result, it was found that the standard deviation and the maximum error of the developed radiation thermometer from the values measured by thermocouples were less than those of an ordinal single-wave thermometer.

Modern technologies and opportunities present new challenges and set new tasks for us. The main components of the smart production of an actuator (so-called smart drive production factory) are different kind of optical sensors. With their help can be provided not only control of structural survey of the smart drive production factory but also the access control system. The main types of optical sensors, their pro and contra and the development of the way they are used are described in the paper.

The most utilized laser scanners, galvanometer-based or with polygonal mirrors produce non-linear scanning. This is a major issue of these devices, as for most applications a constant scan speed (therefore a linear scanning) should be provided. While common linearizing solutions include for example expensive F-theta lenses, we study a simple, lowcost solution, with a two-mirror angular device – in order to linearize the scanning function by increasing the distance between the scanner and its objective lens (i.e., by using an objective lens with an as high as possible object focal length) in a compact solution. By using supplemental mirrors, this object focal length can be folded in order to minimize the dimensions of the assembly. We have used in a previous study a classical approach to this problem. In the present one we propose another method to solve the problem of the total number of images produced by the two-mirror device, as well as the maximum scanner-to-lens distance that can be introduced by the device. The impact of the constructive parameters of the device on these characteristics is pointed out. Design conclusions can be drawn from this study.

Collisions of gas molecules with the walls of small pores in nanoporous materials can cause the width of gas absorption lines to become wider. Also, the effective absorption path lengths through the gas become longer due to multi-scattering within the nanoporous materials. GAs in Scattering Media Absorption Spectroscopy (GASMAS) is an effective technique that can differentiate between the absorption from the gas within pores and the absorption from the bulk of scattering materials. A Vertical-Cavity Surface-Emitting Laser (VCSEL) emitting around 760 nm is used to investigate the absorption from molecular oxygen gas trapped within mesoporous alumina Al2O3. The pore size of the alumina samples are also characterized based on Barrett, Joyner and Halenda (BJH) method. In this work, we will present the correlation between the pore sizes of the mesoporous alumina samples the width of the absorption line of molecular oxygen gas under different experimental conditions.

An Image Sensor Module (ISM) comprises an Image Sensor Chip (ISC) that typically does not contain information (ISC ID) about the manufacturer and specific process, as well as the data for failure analyses. Similar dice by different manufacturers may differ from each other by their quality and lifespan. Counterfeit ISMs usually exhibit lower performance and quality than the original ones. Installing a counterfeit ISM in an imaging device may dramatically reduce its functionality and reliability. The standard ISC ID technology assumes disassembly of the ISC from the ISM and reverse engineering, or a special electrical readout system, if the information was written in the embedded non- volatile memory. We suggest a simple ISC ID method that features Luminescent Composition (LC) introduced into the lenses and/or color filters of ISC. Chip identification is performed without disassembling of the ISM. In addition, the use of LC allows extending the spectral sensitivity of the ISM with silicon image sensor dice. The design is patented (US10210526) and ready for implementation in the new ISM generation.

In this paper, the impacts of surface plasmon resonance (SPR) on the angular spin splitting of light are investigated theoretically. The expression for the angular spin splitting shifts is derived, and the angular shifts as the function of the angle of incidence under different metal film thicknesses are calculated. The simulation results manifest that the angular spin splitting is significantly enhanced when surface plasmons are strongly excited. Under the optimal parameter conditions, the largest angular shift is up to 4.493×10^-5 rad. It is also found that the directions of spatial propagation of photons in the out-of-plane can be switched by adjusting the angle of incidence under certain conditions. These findings may provide a new way for photon manipulation and open another possibility for the development of new nano-photonic devices.

Brillouin fiber sensors permit to perform distributed temperature and strain measurements along an optical fiber through the changes of the Brillouin Frequency Shift (BFS). In conventional Brillouin schemes operating in the time-domain, the BFS is detected by analyzing the interaction between a pulsed pump wave, and a counter-propagating probe wave. The duration of the pump pulse determines the spatial resolution, which however is limited to about 1m due to phonon lifetime. Alternatively, Brillouin optical frequency-domain analysis (BOFDA) and Brillouin optical correlation-domain analysis (BOCDA) configurations provide cm-scale, or even mm-scale distributed sensing capabilities. In particular, BOFDA sensors make use of a continuous wave (CW) pump wave with superimposed a small-signal modulation. The analysis consists in determining, by use of a vector network analyzer (VNA), the amplitude and phase of the corresponding modulation induced on the probe wave intensity, over a discrete number of modulation frequencies. In BOFDA sensors, spatial resolution can be improved down to the cm-range or mm-range, thanks to the pre-activation of the acoustic wave involved in the scattering process. In this work, we show that mm-scale spatial resolution can be exploited, in a BOFDA configuration, to perform both physical (temperature) and chemical (refractive index) sensing. For the latter, a sidepolished fiber was used in order to make the BFS sensitive to the surrounding refractive index (SRI). A sensitivity of the BFS to the SRI as large as 293 MHz/RIU at n_sm = 1.40 is demonstrated experimentally and validated numerically.

Nowadays, lidar is widely used in many atmospheric applications by taking advantage of the properties of laser sources and the progress made, both in the development of new photodetectors and in the sophistication of signal conditioning and processing. Wide dynamic range is an essential feature for atmospheric lidar when the backscattered laser signal varies over many orders of magnitude. Therefore, the lidar detection chain must incorporate a device that ensures this important feature. This can be performed using a variable amplification stage in the electronic detection chain. The amplification circuit developed consists of a low noise preamplifier LNP) cascaded with a variable gain amplifier (VGA). The amplification circuit can be then operated in several gain modes, which enables a wide range of input signals to be processed over several orders of magnitude (~10⁵). Low noise, high speed, linear response and stability are the main specifications pursued during the design. The amplification circuit is a main part of the optoelectronic detection chain that consists mainly of a receiving optics, a photodetector (Si APD), a low noise preamplifier (LNP: 20 dB / 300 MHz / 0.7 nV/Hz^1/2), a variable gain amplifier (VGA: 0 – 60 dB / 375 MHz / 1 nV/Hz^1/2) and a fast analog-to-digital converter (ADC: 20 MHz / 12 bit). Noise, which can significantly affect the performance of the detection chain, is discussed along with the techniques used to reduce it. In addition, noise equivalent power (NEP), signal-to-noise ratio (SNR) and detection limit achieved are presented.

Laser micro-Doppler information generated by characteristic motion such as target rotation or vibration is a fingerprintlike feature of a target such as a vehicle/pedestrian. By combining with the Doppler information, it can be used for the classification and accurate identification of traffic participants. Meanwhile, optical sensor based on such technology is easy to integrate with intelligent driving platform or intelligent traffic monitoring and control platform. This paper proposes a laser Doppler and micro-Doppler composite signal simulation scheme based on vehicle vibration characteristics. Laser Doppler and micro-Doppler composite signals in a platform state simulated by a horn and a onedimensional mobile platform, and a reformed smooth pseudo-Wigner-Ville distribution analysis program is prepared for analysis. Based on this, vibration and motion information are extracted, the laser echo signals are constructed effectively, and physical simulation for composite signal of optical sensor are able to perform.

Indirect monitoring of room's occupancy are two of the key requirements for technological systems that are used to secure independent housing for people in their home environment. For indirect monitoring of the Smart Home room's occupancy, we used Fiber Bragg grating sensor, temperature sensor T(°C), CO₂(ppm) sensor, and humidity sensor rH (%). The first part of the paper describes the proposal of an implementation of Fiber Bragg grating for the detection of human presence in a room of SH. The second part of this paper dealing with the use of CO₂ concentration measurement for detecting and monitoring room's occupancy with the implementation of Artificial Neural Network for the detection of human presence in the room of SH. Experimental results verified high method accuracy (<90%) within the short-term and long-term experiments. Utilization of Fiber Bragg grating in SH was proven on the experimental basis with the combination of measurement CO₂ for room's occupancy monitoring in SH.

Standard reference ring is high accuracy internal diameter artifact which is used as calibration standard in calibration laboratories and industrial facilities. The national metrology institute (NMI) has the task of guaranteeing traceability of measurements within the country with the highest accuracy. All NMIs coordinate with bureau international des poids et mesures (BIPM) to get recognition of calibration and measurement capabilities (CMC). According to the BIPM database (www.kcdb.bipm.org), only 35 of 157 countries have CMC of internal diameter measurement, while 93% of them have uncertaintiy values above 100 nm. This fact shows unequality of measuring capabilities among the countries in the world. To face the issues, this work has done to fullfill the needs on high accuracy internal diameter measurement. Noncontact method is well known as high-accuracy measurement method instead of contact method. The use of optical probe excludes such effect as the deformation of the artifacts and the mechanical probe diameter effect as well. Another thing that we improve is usage of He-Ne laser stabilized with I2 measurement system to increase the accuracy and to reduce the uncertainty. This research explained the uncertainty sources of the method applied and the efforts that has done to reduce it to 50 nm. Finally, this research is very useful for industry, research institutions and the practitioners of metrology at NMIs to improve their internal diameter measurement system accuracy.

Nowadays fiber optic Raman distributed temperature sensors (RDTS) are broadly used for e.g. fire detection, gas leaks detection in pipelines and aircraft icing monitoring. The most common sources of probe pulses for RDTS are CW lasers with external intensity modulation or Q-switched lasers with a pulse duration of several tens of nanoseconds which limits the RDTS effective spatial resolution to a few meters. In this paper we have developed an Er-doped ultrashort pulse (USP) mode-locked fiber laser and implemented it to Raman distributed temperature sensor.This feature allow us to achieve high spatial resolution (down to several centimeters) and high signal-to-noise ratio in the receiving system. An all-fiber erbium-doped laser of 180 fs pulse duration and an average output power of 30 mW was used as a source of probing pulses. We have studied limiting factors of fiber sensor effective length such as high pulse repetition rate of 12.2 MHz and intensity noise of the USP laser (relative intensity noise RIN ~ 6.3 ∙ 10^-4). Furthermore, the peak power of the USP laser has to be at kW level to get high signal-to-noise ratio in the receiving system and pulse duration < 100 ps at full-width-half-maximum for desirable spatial resolution of ~2 cm. Moreover, we have developed an experimental prototype of RDTS with the spatial resolution of ~ 0.1 m limited by the receiving system according to the detector bandwidth of 2 GHz, the effective sensor length of 3 m and ±1.5 °C temperature measurement error. As a result, a list of requirements for a new laser source for distributed temperature sensor was formulated.

Persisting in the large trend to enhance the Near-field Scanning Optical Microscopy and the detection of evanescent waves, a silicon Schottky diode, shaped as a truncated trapezoid photodetector, and sharing a subwavelength pin-hole aperture, has been designed and simulated. Using Finite Elements Method and 3D advanced simulations, the detector has been horizontally shifted across a vertically oriented Gaussian beam, which is projected on top of the device. Electrooptical simulations have been conducted. These results are promising towards the fabrication of a new generation of photodetector devices.

A reflective fiber optic sensor based on multimode interference for the measurement of relative humidity (RH) is proposed and experimentally demonstrated. The proposed probe is fabricated by fusion-splicing, approximately 30 mm long coreless fiber section to a single mode fiber. A hydrophilic agarose gel is coated on the coreless fiber, using the dip coating technique. When the incident light comes from the SMF to the CSF, the high-order modes are excited and propagate within the CSF. These excited modes interfere with one another as they propagate along whole CSF length, giving rise to a multimode interference (MMI). Since the effective refractive index of the agarose gel changes with the ambient relative humidity, as the environmental refractive index changes, the propagation constants for each guided mode within the CSF will change too, which leads to shifts in the output spectra. The proposed sensor has a great potential in real time RH monitoring, exhibiting a large range of operation with good stability. For RH variations in the range between 60 %RH and 98.5 %RH, the sensor presents a maximum sensitivity of 44.2 pm/%RH, and taking in consideration the interrogation system, a resolution of 1.1% RH is acquired. This sensor can be of interest for applications where a control of high levels of relative humidity is required.

In sensing applications utilizing the effect of surface plasmon resonance (SPR), a thin film of gold is widely used as the plasmonic layer. Despite advantages of gold over other metals, characterization of its optical properties is not sufficient as is evident from the measured responses at different angles of incidence. In this paper, a new method of determining the optical constants of a thin golden layer is presented. The method is based on measuring the phase shift between p- and s- polarized optical waves induced by SPR for air in the Kretschmann configuration with an SF10 glass prism and an SPR structure. The SPR structure comprises a gold coated SF10 slide with a chromium adhesion layer. In addition, a birefringent crystal is included in the setup to attain the spectral interference. Information about the phase shift induced by SPR is inscribed in the spectral interferogram recorded by a spectrometer and can be retrieved using the Fourier transform analysis. The measurements are performed for different angles of incidence to obtain the spectral dependence of the optical constants of the golden layer. Measured data are fitted to a model and in addition, the feasibility of the method is demonstrated in measuring the phase response for distilled water.

Optical spatial frequency (correlation) filtering techniques identify a class of noncontact vectorial velocity sensors. Detectors according to this optical measuring method are characterized by a fast measurement with a small dead time and low measurement uncertainty. For the purpose of measurement, the sensors determine the relative displacement of any randomly structured surface with respect to the sensor. The use of newer filter structures can reduce the measurement uncertainty.

Often, optical devices require resonators with a limited set of natural frequencies and an equidistant spectrum. These requirements are satisfied by ring confocal resonators. Such resonators can be manufactured as a single monolithic element (prism) and used, in particular, as sensitive elements of miniature optical gyroscopes. As a result of external mechanical and thermal effects and imperfection of manufacturing technology, the reflecting surfaces of ring confocal resonators can be misaligned. This paper is devoted to the analysis of the effect of these misalignments on the optical properties of resonators. OOFELIEMultiphysics software is used to calculate the deformations arising in the resonator as a result of external effects. The influence of the deformation of the resonator on its optical properties is estimated using the modified method of Fox and Lee.

Due to external cavity, the external-cavity diode laser (ECDL) is sensitive to the harsh environment. It can serve as a very convenient tool for measuring or comparing acoustic responses and analysis of acoustic insulation characteristics of materials and mechanical structure. Focused on the ECDL, improvement of the laser acoustic responses and suppression of the laser system drift are critical. But the acoustically-induced vibration coupled with complex disturbance will contribute to the frequency fluctuation, therefore it is difficult to investigate the dynamic response characteristics of laser frequency to acoustic signals separately. In order to decouple the acoustic response from environmental noise and to reduce system drift, a frequency stabilization system by virtue of grating feedback and current feedback is demonstrated with the a wide-bandwidth loop. After recording the system response, the amplitude-frequency characters are achieved through fast Fourier transform (FFT). After analyzing the correlation of the laser frequency fluctuation and the acoustic stimulant signal’s frequency, the acoustic dynamic response characteristics of the ECDL is depicted experimentally. By contrasting the acoustic response characteristics of the ECDL with or without the acoustic proofing case, the acoustic insulating effect could be mapped directly. The experimental results show that the acoustic proofing case can not be remained valid for all frequency bands effectively. It can also act as the experimental criteria for optimizing the design of laser mechanical structures and acoustic insulation systems. Furthermore, this optical system could be employed as a detector extending to acoustic sensing or acoustic precise measurement.

A theoretical study of a new type of surface electromagnetic wave sensor, similar to a surface plasmon resonance (SPR) sensor, which utilizes a one-dimensional photonic crystal (1DPhC) instead of a metal film, is presented. Replacing the metal film in the SPR sensor by the 1DPhC has number of advantages including physical and chemical robustness, enhanced sensitivity, etc. 1DPhCs can be engineered to exhibit metal-like optical properties over given frequency intervals. Equivalently, the optical response of the 1DPhC can be described by an effective dielectric constant with a negative real value that permits the 1DPhC to support surface electromagnetic waves at frequencies within the forbidden transmission band. In our theoretical study, the 1DPhC is represented by a multilayer interference filter and we model the response of the system comprising a BK7 prism/multilayer/analyte in a Kretschmann configuration. For the system under study we express the reflectances of p- and s-polarized waves as a function of angle of incidence on the prism. Dips in the reflectance spectra represent the coupling of light waves to surface modes and this can be confirmed by sensitivity to refractive index changes at the multilayer-analyte surface. The theoretical study is accompanied by experiment with some results for the BK7 prism/multilayer/analyte system in the Kretschmann configuration.

Optical tweezers use a special class of light beams – the so-called Bessel beams. The field amplitude of these beams is described by the Bessel function of the first kind of a zero order. The traditional method of forming zero-order Bessel beams involves the use of a classical optical element – a conical axicon lens. We designed and assembled an experimental test bench to study the parameters of the Bessel beam formed by the axicon. In the course of experimental studies, it was confirmed that Bessel beam is a diffraction-free beam. In addition, an influence of a divergence of the Gaussian beam at the axicon input on the parameters of the Bessel beam was investigated. The transformation of such a beam by an optical system was considered. It is shown that when the Bessel beam is transformed by an optical system, the principle of similarity of optical fields in the optical conjugate planes is fulfilled. The results of modeling the formation of the Bessel beam by the axicon obtained in this work are consistent with the experimental studies.

Magnetic field sensors have been widely applied in several areas, for instance, in navigation, geophysical, aerospace engineering and biomedical research. The traditional methods used to sense this parameter have drawbacks related with size, stability, multiplexing capability, remote measurement and electromagnetic sensitivity. Due to the characteristics inherent to the optical fiber, including small dimensions, immunity to electromagnetic interference and the possibility of being used in hazardous environments, this technology has great potential for sensing different parameters. In this work, the magnetic field was monitored using a Fabry-Perot micro-cavity. The cavity, produced from the recycling of optical fiber previously destroyed by the catastrophic fuse effect, was filled with magnetic fluid (MF). Then, it was exposed to a magnetic field in the range of 0 to 200 mT, applied transversally to the fiber axis. An overall exponential decrease of the wavelength of the reflection spectrum with the increase of the magnetic field was obtained, with a sensitivity and resolution of 120.5 ± 4.4 pm/mT and 8.3 μT, respectively, in the range of 0 to 80 mT (linear behavior). The proposed sensor represents a cost-effective solution for the magnetic field sensing, with an improved performance compared with other devices already reported in the literature.

This study presents an ultra-sensitive carboxyl-functionalized graphene oxide (GO-COOH)-based surface plasmon resonance (SPR) immunosensor using Carbohydrate antigen (CA) 199 (CA199) biomarker to detect pancreatic cancer. A study of the effect of carboxyl-GO-based biocompatible composites with protein on sensing adhesion and diagnostic engineering is an useful technique. The optical and sensing properties of carboxyl-GO sheets improved sensitivity and affinity for molecular detection of biomarker. In the experiment, the SPR biosensor with carboxyl modified graphene oxide as substrate was tested to detect the immune response of CA 199. The literature indicates that 79% of pancreatic cancer patients have carbohydrate antigen 19-9 content above 37 unit/ml. The experimental results show that the lowest antigen detection limit of surface plasmon resonance biochip with carboxyl modified graphene oxide as the substrate can reach 10 unit/ml.

A method for high-sensitive measurement of optical power of fiber lasers is introduced. It is based on application of a metal-coated fiber as a sensor. A part of optical radiation transmitting through the core of a metal-coated silica fiber is scattered and further absorbed in the outer cladding. The change of electrical resistance of the metal coating induced by its heating is measured. This technique can be used for measurements of the output power of fiber laser sources in real time with minor optical losses and beam distortion. The dynamic range can be widely varied by changing the bend curve radius of the sensor fiber. Optical scattering and bend losses were investigated for different geometries of metal-coated fibers. A heating model of metal-coated fibers was developed.

Analysis of gait pattern of individuals is a very useful tool for the identification of locomotive motor anomalies, which can lead to early diagnosis and adequate treatment of patients with motor disorders. The knees are the lower limb joints exposed to major tension during human locomotion, presenting higher risk of a wider range of possible disorders. The devices used to monitor human joints should be comfortable and not restrain patients’ movement, while maintaining their resolution and accuracy. Most of current measurement techniques are based on electronic devices, which are often not adequate for demanding environments, such as the context of physical rehabilitation. We propose an e-Health sensing solution to dynamically monitor human knee angles during gait, using low-cost intrinsic Fabry-Perot interferometers optical fiber sensors (FPI-OFS). To the best of our knowledge, no previous efforts have reported the use of FPI sensors for such dynamic monitoring. The overall sensor consists of an optical fiber containing the FPI microcavity, which is embedded along the longitudinal direction of a kinesio tape (K-Tape), and placed along the knee rotation axis. Since the K-Tape has great adhesion to the skin, the FPI sensor is kept at the knee rotation axis, without restricting the user’s movements. During the knee flexion/extension, the K-Tape extends/compresses accordingly, resulting in the modulation of the reflected spectrum by the FPI-OFS. Several calibration and performance tests have been performed. Their results show the reliability and accuracy of the proposed solution, with sensibilities values of 53.8±2.4 pm/°.

We propose a novel hemoglobin fiber-optic sensor which is based on the evanescent field of side-polished fiber. It is functionalized with a thin-layer of a hemoglobin-sensitive graphene oxide (GO) coating on a side polished optical fiber. The trace of hemoglobin concentration was measured by the variations in transmitted light intensity and the optical properties of graphene oxide. The sensor output was obtained successfully in response to hemoglobin concentration and sucrose concentrations. The side-polished fiber with GO film exhibited real- time and remote measurement of hemoglobin concentration with high precision.

The traditional surface plasmon resonance (SPR) instrument has the advantages of real time, label-free and high sensitivity. This study mainly makes the traditional SPR instruments miniaturized into active plasmon colorimetric biosensors, which is used for point of care and further improve the medical Level. Nano-printed technology is a simple process technology that used in the preparation of nano-structure with advantages of low cost and high production, for the future active plasmon colorimetric biosensors manufacturing has a very high Production advantages. Organic light emitting diodes have the uniformity of light intensity at different angles, which is one of the indispensable conditions in the detection process of plasmon bioassay. In this experiment, it is proved that the grating period is 555 nm, when the refraction value change from 1 to 1.33 the coupling wavelength shifted about 190 nm, the minimum refractive index is 1.736×10^-3 RIU. The binding reaction with β-hCG (1 μM) was enhanced by the bonding of Peptide (1 mM) with gold nanoparticles (15 nm), which was about 43.88 times higher than that of the original peptide (1 mM) and β-hCG (1 μM). That the minimum refraction value of the change in the sensitivity increased to 3.956×10-5 RIU. After the peptides (33 nm) bonded Peptide (1 mM) and β-hCG (1 μM) were used for the active plasmon colorimetric biosensors. The plasmon at a measuring angle of 5° wavelength of the emission shifted 16 nm, and the measurement angle is 4 nm at the measuring angle of -5°.

An original concept of optical sensing is presented. It assumes detection of differential spectral characteristics of the analyzed object, in particular the spectral derivative. This approach provides direct discrimination of local spectral features (lines of emission, absorption Raman scattering) from the smooth background. The concept is realized with original spectral instrument based on acousto-optical tunable filter operating in modulation mode. Rapid modulation of ultrasonic wave provides inhomogeneous oscillating Bragg grating. It is demonstrated that the component of the periodical photodetector signal selected by phase-sensitive technique at the modulation frequency is proportional to the spectral derivative value at the wavelength of the filter. This optical sensing method does not require spectral recording and further derivative calculation. Therefore, it is promising in spectral imaging applications for real-time acquisition of images rectified from the background.

Long-term and continuous health monitoring of structures is of essential interest within the civil engineering communities due to the aging of infrastructures. Detect defects and monitor various physical or chemical parameters related to the health of the structures is vital for safety evaluation and health monitoring allowing for decision-making in terms of maintenance and retrofitting. Among the parameters of interest, the deflection is one of the most important parameters because the deflection limit is usually utilized as a control index of structures when subjected to potential external loads. However, it is not easy to have a real-time structural variations measurement because of the difficulties in measuring the deflection directly. Indeed traditional direct techniques, like dial indicator, level, and total station, have limited discrete points and are suitable only for short term monitoring. While newer whole field techniques, like accelerometer, microwave interferometer, GPS, connected pipe optoelectronic liquid level sensor, are developed for real time deformation measurement, but they need to install additional setup that causes extra costs and measurement data. An alternative approach for monitoring the deflection of the structures is based on an indirect measure such as the strain with attachable sensors and using proper transformation to estimate the displacement field. Along this line of argument, Fiber Bragg Gratings (FBGs) are good alternative to strain gauges and in the last years a demonstration of the deflection monitoring has already been carried out limiting the attention to one dimensional structures. Thus, in this paper, we extend and generalize the deflection estimation to a multilayer bidimensional structures by using FBG strain sensors and a displacement-strain transformation. In particular, several FBGs have been embedded in the structure within only a few optical fibers, thus avoiding the complex wiring typical of strain gauges. Then, from the strain measured by the FBGs, the curvature function has been evaluated as a polynomial function whit the coefficients obtained by least mean square; and the deflection is estimated by integrating twice the curvature function. Experimental results show good agreement with those directly measured by a dial. The proposed technique allows a real-time indirect structural monitoring solving the existing difficulties in measuring the deflection directly, and can be applied to small as well large structure. Furthermore, it is crucial in high energy physics, where particle bidimensional detectors have to measure the position of the incoming radiation with a resolution of few tens of microns, and detectors deflection directly influences this measurements.

The pace of development of information systems nowadays demonstrates the magnitude of the demand for digitization of all aspects of our lives, such as medicine, industry, and documentation of cultural heritage. Digitization is the process of converting objects from the real world into their digital representations. In order to acquire complete and detailed information about the whole surface of an object, several 3D scans have to be taken from different perspectives. The resulting 3D object can be acquired in a form of a numerous amount of 3D point clouds overlaying each other. Sometimes, depending on a quality of a 3D scanner and surface properties, the point clouds can represent a noisy geometrical surface and an incorrect colour. Moreover, the directional point clouds are not perfectly aligned and a registration between them must be applied. The registration of the point clouds is a complex task which is not always possible to automate. Usually, the entire process of registration has to be supervised by a skilled operator. The registration is usually divided into two parts: initial and final matching. Initial matching is a more complex one and in this scenario, it is supported by the known system calibration, which includes, e.g., robotic arm, head of the scanner, sources of lights. Using ICP based algorithms afterward is usually enough to get appropriate final matching. The difficulty of point cloud registration increase accordingly to the number of directional clouds of points to integrate. The aim of this paper is to propose a methodology to decrease or even fully eliminate some of the presented registration issues encountered during the reconstruction of Museum of King Jan III’s Palace at Wilanów.

With the rapid development of image sensor research, mobile industry processor interface (MIPI) was used to meet the massive data throughput capacity since the higher frame rate and more pixels on the smaller sensors. This paper realized the image processing of MIPI based on FPGA. The image sensor used here is OS08A10, which has 8Mega Pixels and contains up to 4-lane MIPI serial output interface. The resolution of image sensor is 3840*2160 at frame rate of 25fps and each pixel is 10 bit, so the data throughput is 2Gbps. Since the FPGA used in this project is Spartan 6 series and it cannot deal with MIPI data directly, it is necessary to change these MIPI data into LVDS data beforehand. After receiving the processed sensor data, FPGA stores these data into DDR3 and output them through HDMI for display. The result shows that the data transmission and process of MIPI is stable and reliable which can be widely used in other MIPI sensor control.

We describe a non-invasive and non-contact viscosity measurement system using a compact optical fiber heterodyne interferometry. The proposed system consists of a fiber based pulse laser for surface acoustic wave (SAW) excitation and a lensed fiber for probing laser. When the pulsed laser illuminates onto the oil surface, the SAW is generated by photoacoustic effect and it propagates along the surface. The interference of probing laser reflected on the sample surface has the information of the surface movement. We can calculate the propagation velocity of SAW from the detected interference signal. The propagated SAW contains the information of liquid properties (viscosity and elasticity). For the preliminary measurements, an industrial engine oil and a polydimethylsiloxane (PDMS) are used. We can measure the viscosity of them without noncontact, successfully.

A novel method of optical image registration using matrix of piezoelectric crystals is introduced. This technique allows measurement of beam profiles without using attenuation systems even at high power levels of incident radi- ation. Each element of the sensor matrix is the crystal piezoelectric resonator that has its own set of eigenmodes, which frequencies strongly depend on temperature. Due to an inverse piezoelectric effect the eigenmodes can be excited noncontactly via the application of the probe radiofrequency electric field providing that its frequency corresponds to any of the crystal eigenmode frequencies. Due to the residual optical absorption each element is heated in compliance with the incident radiation power. A calibration procedure is preliminary performed by transmitting collimated laser radiation separately through each single matrix element.

The recent results about the fabrication and characterization of Long Period Gratings (LPGs) in different pure silica optical fibers by means of Electric Arc Discharge (EAD) technique are reported in this work. Nowadays, LPG in standard fiber represents a unique platform for physical, chemical and biological sensing whereas specialty optical fibers permit to extend the use of fiber optic technology to unconventional applications. For instance, pure silica fibers are appealing in high energy applications. Here, we take into consideration two fibers with pure-silica core having significant differences in physical and geometrical design. The first one presents a micro-structured pure-silica cladding, photonic crystal fiber, and the second one shows a solid Fluorine-doped cladding. EAD leads to a point-by-point LPG inscription, due to localized tapering of the transversal size of the core and cladding regions along the fiber, and to changes of the silica refractive index due to the stress relaxation induced by local hot spots. The aim of the work is to identify an appropriate “recipe” for each fiber, to fabricate LPGs with strong and narrow attenuation bands and trivial power loss. Indeed, a proper combination of arc power and duration, as well as fiber tension, allows for the appropriate core and cladding modulation and thus for the desired LPG spectral features. The sensitivity characteristics towards surrounding refractive index (SRI) and temperature changes of these LPGs are also investigated.

We present an optical fiber device involving metal-dielectric colloidal crystal (MDCC) structures as a platform for surface enhanced Raman-scattering (SERS) sensing applications. The MDCC structures received large interest in last years since they permit to combine localized surface plasmonic resonance (LSPR) of noble metallic nanoparticles and photonic bandgap (PBG) of colloidal type photonic crystals (PhCs). Most of the MDCC structures have been provided onto planar substrates and then investigated as SERS platform. However, the integration and/or combination of the advantages MDCC structures with optical fiber technology represent still open challenges. The present paper reports recent results about MDCCs fabricated directly onto fiber optic tip surface by successive depositions of Au-NPs on PSbased CCs. Our goal is the fabrication of miniaturized fiber optic devices for SERS sensing applications. Numerical and experimental results of different samples are here presented and discussed. For the sensing test, the fiber probes were immersed in a 100μM ethanol solution of 4-Mercaptobenzoic acid (4MBA). Then, preliminary SERS results were retrieved by a Labspec Aramis confocal Raman spectrometer.

Infrared photoresponse in large area MoSe₂ nanostructured films on flexible substrates has been presented in this work. Nanostructures of MoSe₂ have been grown by hydrothermal route using sodium molybdate and selenium (Se) as a precursor in hydrazine and water solution. The process parameters such as ambient pressures and temperature have been optimized to get the nanostructure with superior photosensitivity in IR regime. The adopted synthesis process results in the suspended particles composed of MoSe₂ nanostructure, which later transfer in ethanol. This solution has been coated on flexible poly-ethylene terephthalate (PET) substrates for the device fabrication by dip coating. Scanning electron microscopy and high-resolution transmission electron microscopy (HR-TEM) reveals that the as-prepared MoSe₂ has particle-like features. The photoresponse of the devices was measured in the wavelength range 1000 nm -1600 nm. As-obtained flexible photodetectors showed responsivity of ~ 2.6 A/W (at 500 mV bias) and rise/fall time 3.9 sec and 2.9 sec under the illumination of 1550 nm. It was also noted that for the small bias voltages, our MoSe₂ films possess excellent photoresponse as the at 50 mV bias the responsivity was recorded up to 127 mA/W for 1550 nm light). The simple approach used in this work should facilitate the development of low cost and low power IR photodetectors for next-generation flexible optoelectronics.

A surface plasmon resonance (SPR) based fiber optic sensor is simulated and analyzed in near infrared (NIR) region for normal (N) and malignant human liver tissue (MET) detection. Proposed five layered sensor consists of samarium-doped chalcogenide core, silver layer (Ag) deposited on the polymer clad, followed by graphene monolayer and analyte layer. Transfer matrix method for N layer model has been used for normalized reflection coefficient (R) calculations for the proposed multilayer structure. Furthermore, sensor structure utilizes the selective ray launching where incident angle (α) is varied at fiber input end (angular interrogation) and power transmitted through sensing region of length ‘L’ is measured in dB. At resonance (i.e., α = αSPR), sharp power loss peak is obtained where, αSPR shifts to other angle (i.e. δαSPR) with a change in analyte refractive index (RI). The prime focus of the present study is to optimize the radiative damping (i.e., optimum radiative damping (ORD)) at Ag-graphene junction to bring significant enhancement in the sensor’s performance. At resonance condition, the interference between incident light and back-scattered light known as radiation damping is responsible for excessively large sensor’s figure of merit (FOM). Hence, the coupled role of metal layer thickness (d_m) and wavelength (λ) with 2D material layer plays important role as extent of radiation damping changes significantly, which leads to massive increase in FOM. For the proposed sensor structure value of L/D is taken as 25 (D represents the fiber core diameter) achievable with various L and D combinations (e.g., L = 1 cm and D = 400 μm). The combination of dm = 35 nm and λ = 865 nm leads to a maximum FOM of 4910.32 RIU^-1. The coupled effect of dm and λ leads to significantly higher value of FOM, enables the graphene-based fiber-optic sensor for biosensing and other applications.

Avalanche Photodetectors (APDs) with high dynamic ranges are tested with scanning microscopy to reveal their sensitivity towards the components optoelectronic spatial design. The measurement will unveil design flaws of typical APD design approaches and suggest improvements. In the end, the specification of the component will be discussed under the issued findings. optical induced current.

The article describes a comparative measurement of a classical seismic sensor and a fiber-optic interferometric sensor for the perimetric applications. We created and proposed technically and financially the simplest interferometric sensor (type two-arm Mach Zehnder). A test polygon was created where were analyzed the vibration-acoustic manifestations caused by the 20 test subjects. The article describes original results that clearly point to the high sensitivity of the interferometric sensor.

In this work we present the investigation of the interaction of fibronectin with different biomaterials. Since the amount, type and possible conformational changes of adsorbed proteins at the body-implant interface strongly influences the performance of implants, this work is focusing on a more comprehensive understanding of these processes. To create very stable and thin surface modification of a glass transducer with PEG, PU and PLA an immobilization strategy based on silane chemistry was developed. To monitor the adsorption and desorption of fibronectin onto these biomaterial surfaces, the reflectometric interference spectroscopy – a direct optical method – was applied. To estimate the association and dissociation rate constants, a biomolecular interaction analysis was performed within the kinetically limited regime of the association process. Additionally, the influence of the pH value on the adsorption behavior is exemplary shown for the interaction of fibronectin on a glass surface. These experiments show high potential to give more detailed insights into the complex processes during the implantation of foreign materials into the human body.

This work reports the development of a bioinspired sensor capable of measuring vertical and shear (tangential) forces. The sensor is composed of two materials, the polylactide (PLA) and epoxy resin, combined with a photosensitive optical fiber with two fiber Bragg gratings (FBG1 and FBG2). The FBG1 was placed in a cavity filled with epoxy resin, while FBG2 was between the cavity and the shear wall that undergoes shear force. This FBGs’ encapsulation allowed one of them to be affected by vertical and shear forces (FBG1), while FBG2 was only affected by shear force. The calibration and performance tests were carried out with the aid of an electronic tri-axial force sensor. From these tests, sensitivities of K1V= 0.02±2.35x10^-4 nm/N; K1S= 0.13±3.25x10^-3 nm/N; K2V= -2.88x10^-4±6.72x10^-5 nm/N and K_2S= -1.77±0.03 nm/N to each type of force, for FBG1 and FBG2, respectively, were achieved. The obtained results demonstrated the reliability of the developed solution, with a significant improvement of its sensitivity to shear force, and a low production complexity, when compared to other previously reported optical sensors.

Plastic Optical Fibers (POFs) are becoming popular for the development of sensors with multiple applications. In this work, we report a preliminary study related with the coating of modified POFs with proteins. Samples of POF were immersed in buffer and in proteins’ solutions under different experimental conditions: modification of the POF sample, immersion time, temperature, buffer solution and concentration of protein. A simple and easy methodology using protein staining solution was performed to confirm the coating of the POFs with proteins and to evaluate the dependency with the experimental conditions. Further developments will be focused on the coating of POFs with modified proteins for the selective detection of contaminants in water contributing to the development of low-cost POF chemical sensors and biosensors.

The understanding of nanoscale biological processes is limited by the level of details we can achieve when observing their dynamics. Addressing molecules of interest using fluorescent labels is the most common contrast mechanism in biological nano-imaging. However, the complex photophysics of fluorescent labels limits the localization precision as well as observation times in practical experiments. As an alternative to fluorescence-based microscopy interferometric scattering microscopy (iSCAT) was recently introduced. It is an optical microscopy technique allowing to detect and track nanoscale objects with sub-nanometre localization precision. The basic concept of this technique is the interference of light scattered on the particle with a reference wave light partially reflected at the microscopic slide. Recent advancements pushed the sensitivity and high-speed tracking down to a level of a single unlabelled protein by balancing the amplitudes of scattering and reference waves. This is often achieved by optimizing the reference wave, e.g. via placing a partially transparent mask near the back focal plane of a high numerical aperture microscope. In this contribution we introduce and demonstrate an innovative layout of the iSCAT microscope with optimized reference wave and minimized interferometric artefacts. We benchmark the detection capabilities of the new layout using series of extremely small spherical gold nanoparticles and demonstrate possible applications of the novel detection scheme.

Three methods of multimode fiber interferometer signal averaging are investigated theoretically and experimentally: the ensemble averaging, the averaging over a long realization, and the averaging over transverse coordinates of an output speckle pattern. The analysis is performed for two wavelengths and two launch conditions of the graded-index multimode fiber: few mode and multimode. Applicability of methods for practical applications is discussed.

Biology is a fundamental scientific field which has made significant progress over the course of recent centuries and with the help of modern microscopy techniques, major discoveries are still being made today. The time span of processes such as protein dynamics ranges from slow to extremely fast. That is why high temporal resolution has recently become one of the desired parameters in biological experiments. The improvement of ultrafast image acquisition technology can help us to achieve higher temporal resolutions than before and detailed biological processes of rapid nature can now be observed. With these possibilities comes a desire to determine the noise characteristics of ultrafast cameras to set the limitations in localization precision in tracking of biological objects and their labels, which is the focus of this manuscript.

Self-sweeping of laser frequency is relatively new effect in fiber lasers. The effect consists in periodic dynamics of the laser frequency without use of tuning elements and electrical drivers for frequency tuning. Owing to broad sweeping range (up to 23 nm) and simplicity, self-sweeping fiber lasers are attractive sources for applications demanding tunable radiation. Currently the self-sweeping effect in fiber lasers was observed in different spectral regions covering range from 1 to 2.1 μm. However, it is difficult to control spectral dynamics due to self-induced nature of the sweeping effect. In the paper, we demonstrated linearly-polarized Tm-doped fiber laser with lasing near 1.9 μm with manually controlled the spectral dynamics with pump power adjustment. The laser operates in three self-sweeping regimes depending on pump power: 1) with normal scanning direction at high rate (~5 nm/sec) and, 2) with reverse one at low sweeping rate (~0.1 nm/sec) and 3) wavelength stopping. In the case of wavelength stopping, the wavelength can be stopped at arbitrary value in the range from 1912 to 1923 nm depending on prehistory of spectral dynamics of the laser. The wavelength stability in case of wavelength stopping is better than 50 pm within 5 minutes. In the case of linear scanning of laser line, sweeping range exceeds 15 nm.

In this paper, we propose a new iterative process of sorting an array of signals, which differs from the known structures of sorting signals by uniformity, versatility, which allows direct and inverse sorting of an array of analog or digital signals. The basic elements of the proposed sorting structures are simple relational nodes for analogue signals from sensor devices and cameras. Such elements can be implemented on a different element basis, including, on devices for selecting a maximum or minimum of two analog or digital signals, which are implemented, in one of the variants, on CMOS current mirrors and carry out the function of continuous logic limited difference. We offer optoelectronic implementation of such basic relational element and a homogeneous sorting structure on such elements, consisting of two layers and a multichannel sampling and holding device. Nine signals corresponding to a selection window of a matrix sensor are fed to this structure, we sort them in five iterative steps, and at the output we receive the signals sorted by the rank, which, using the code controlled programmable multiplexer, generates an output signal, corresponding to the selected rank. We evaluate the technical parameters of such a relational preprocessor for nonlinear signal processing in image processors, sorting networks, multichannel parallel type sensor, processing, and encoding systems. The base cells consist of no more than 20 CMOS 1.5μm transistors, the total power consumption of the sorting node on 10 continuously logical base cells (CL BC) is 2mW, the supply voltage is 1.8÷3.3V, the range of an input photocurrent is 0.1÷24μA, the conversion cycle is 10μs, but can be improved by selecting other transistors and some modifications of the circuits. Such mixed analog processor is modeled in PSpice OrCad. The paper considers results of design and modeling of CL BC based on photosensitive cells with an extended electronic circuit and current mirrors (CM) with functions of preliminary subsequent analogue processing for creating picture type image processors (IP) with matrix parallel inputs-outputs. Such BCs and sorting nodes based on them have a number of advantages: high speed and reliability, simplicity, small power consumption, high integration level. We consider CL BC for methods of selection and rank preprocessing. In contrast to our previous works here we will dwell more on analogue preprocessing schemes for signals of neighboring cells. Let us show how the introduction of iterative sorting nodes extends the range of functions performed by the IPs. Examples of image processing with proposed preprocessor are simulated in MathCad and show the field of application of such coprocessors and new prospects for realization of linear and matrix photo-electronic structures with matrix operands. The essential difference is that the structure is iterative and allows to significantly reducing hardware costs in comparison with other hardware implementations of sorting networks. We discuss some aspects of possible rules and principles of learning and programmable configuration for the required function, relational work, and the implementation of hardware blocks for modifying such processors.

We introduce new technologies improving the PLD (Pulsed Laser Deposition) method to fabricate visible (370 ~ 600 nm) and NUV (Near Ultraviolet, 185 ~ 320 nm) photocathodes for IIT (Image Intensifier Tube) sensors. The multi-purpose PLD VC (Vacuum Chamber) by utilizing optical window viewports and a couple of internal carousels can do the whole process of the laser deposition of various alkalis, including the measurement the QE (Quantum Efficiency) in-situ, for multiple photocathode targets. Then, we have integrated a Load/Degassing/Assembly (LDA) VC to the PLD VC, to prepare, load, degas, and assemble the alkali targets and the photocathode substrates. With these facilities, we have manufactured high QE photocathodes free from oxidation and water vapor contamination during the process. In this paper, we describe detail procedures of our new technologies to make S20 and CsTe photocathodes for visual and NUV wavelengths respectively, and discuss about the test results of the IIT products.

A highly sensitive and easy-to-fabricate hydrogen sensor based on a plasmonic ‘gold nanowire array on a palladium layer deposited on a metallic substrate' is proposed. Plasmonic waveguide modes are excited in the gaps between the nanowires in this ‘gold nanowire array on a palladium spacer layer deposited on a metallic substrate' system. As incident light is coupled into the plasmonic modes, a dip in the reflectance spectra is observed at the resonant wavelength, i.e., the wavelength at which the incident light is coupled into plasmonic modes. On exposure to hydrogen, the palladium spacer layer transforms to palladium hydride (PdH_x), where x, the atomic ratio of H:Pd, increases as the hydrogen concentration increases. This transformation changes the optical properties of the Pd layer, and hence the position of the resonance wavelengths (λ_res), i.e., the position of the reflection dips in the reflectance spectra of the Au-Pd-Au system, for various concentrations of hydrogen. The difference between the positions of the resonant wavelengths of PdHx and Pd, (λ_res(PdHx)−λ_res(Pd)), is used as a measure of the sensitivity of the proposed hydrogen sensor. Analysis of this shift in the plasmon resonance wavelength is done numerically, using Rigorous Coupled Wave Analysis (RCWA) for various values of d, the side length of the nanowires; t, the thickness of the Pd spacer; g, the gap between the adjacent nanowires and θ, the angle of the incident radiation. It is found that, in the presence of hydrogen, the maximum shift in the resonance wavelength for the proposed sensor is ~41 nm as compared to the case when hydrogen is absent. This shift in the resonance wavelength is higher than many currently employed plasmonic Pd-based hydrogen sensors. Thus, the proposed ‘gold nanowire array on a palladium spacer layer deposited on a metallic substrate' is an easy-to-fabricate, selective and sensitive hydrogen sensor.

This paper presents hybrid plasmonic substrates fabricated by a combination of bottom-up and top-down process of fabrication which can be employed as efficient Surface enhanced Raman scattering (SERS) substrates for chemical sensing. The hybrid approach leads to a cost-efficient fabrication with smaller fabrication times than the pure top-down approach and higher degree of control than the pure bottom-up approach. We demonstrate the achievement of sub-20 nm gaps on a large area with this hybrid methodology. These small gaps lead to the formation of electromagnetic hotspots, i.e., regions of high electromagnetic enhancement. The electromagnetic behavior of these substrates is analyzed theoretically using Finite Difference Time Domain modeling. The sub-20 nm gaps lead to the electromagnetic SERS enhancements of the order of ∼10⁸, and a change in the gap size can tune the plasmon resonance wavelength from the visible to the near-IR region of the spectrum. It is thus shown that these SERS substrates offer high SERS enhancement along with a capability of passive tunability of the plasmon resonance wavelength by changing the geometrical parameters in these substrates.

In this work, we present robust and easy-to-fabricate optical gas and vapor sensors based on optical fiber resonators (OFR) coated with palladium (Pd) thin films, Pd micro-particles and polymer brushes (PB). Pd based sensors are used for hydrogen (H2) gas detection in concentration range of 0% to 1% and polymer brush-coated OFR are used for detection of vapor in concentration range of 0 to 25%. Sensing mechanism of these sensors is based on spectral shift of resonance wavelength which are called whispering gallery modes (WGMs). This spectral shift is due to volume expansion of the sensing material. Tapered fiber is used in order to excite WGMs in coated OFRs. Good sensitivity and repeatability results are obtained for all three types of sensors.

This work addressed the simultaneous retrieval of Land Surface Temperature (LST) and Land Surface Emissivity (LSE) from time-series thermal infrared data. On basis of the assumption that the time-series LSTs can be described by a piecewise linear function, a new method has been proposed to simultaneously retrieve LST and LSE from atmospherically corrected time-series thermal infrared data using LST linear constraint. A detailed analysis has been performed against various errors, including error introduced by algorithm assumption, instrument noise, initial emissivity, etc. The modeling errors of the proposed method from the simulated data are less than 0.04 K for temperature and less than 6.76E-4 for emissivity. The proposed method is more noise immune than the existing methods. Even with a NEΔT of 0.5 K, the RMSE of LST is observed to be only 0.13K, and that of LSE is 1.8E-3. In addition, our proposed method is simple and efficient and does not encounter the problem of singular values unlike the existing methods.

In this work, modelling and simulation of Organic Photo Detector (OPD) is carried out using Finite difference time domain (FDTD) method. By interposing photonic crystals into the OPD, the electric field intensity is significantly enhanced compared to conventional photo detectors. The optical effects such as power absorption is observed by interposing water soluble conjugate polymer layer such as poly(9,9-bis(3’-(N,N-dimethylaminopropyl)-2,7-fluorene)-alt- 2,7-(9,9 dioctyl fluorene)] (PFN) as interlayer into the OPD device structure. Propitious research work is being carried out aiming at increasing the power absorption of OPD. This work proposes an alternative OPD using Gaussian source. The light excitations generates an electron-hole pair increasing the carrier’s density. The resulting electrons in the conduction band and the holes in the valence band can be drifted by an electric field, generating a current. This OPD device has very thin active organic layer less than 100nm. The Photonic Crystal (PC) used in the design has rectangular lattice structure with height of 120nm and width of 350nm. The Finite Difference Time Domain (FDTD) method is used for solving Maxwell’s equations in complex multi stack geometries. FDTD calculates the E and H fields everywhere in the computational domain (evolves in time domain), it provides animated displays of the electromagnetic field movement through the OPD model. The short circuit (Jsc) current obtained for the proposed OPD for with and without water soluble conjugate polymer placed above the emissive and incorporating PC in the device. This ensures high detectivity of the organic photo detector device.

This paper describes a possible design of encapsulation of fiber Bragg grating (FBG) for the traffic applications. We have simulated properties and then created two type of encapsulation of FBG into polymer polydimethylsiloxane (PDMS) and lukopren (carbohydrate binder). Encapsulated FBGs were stored in the created concrete road retarders. These retarders were burdened by the repeating passes of the testing vehicles (10 different vehicles). We analyzed the detection capability of vehicles, compared obtained results and discussed the influence of above-mentioned encapsulation on the FBGs (in case of uses for traffic applications).

In this research, cesium iodide (CsI) optical crystals have been grown for radiation detectors by homemade Bridgman-Stockbarger method. CsI crystals have been innovated for optical properties by applying techniques of Ca doping and multiple doping of Ca and Tl. As a reference; CsI:Tl crystal was also grown in the identical growth system. The crystal growth was processed under argon atmosphere in a quartz crucible. The composition of dopant was kept a constant of 0.35%wt. X-ray diffraction measurements show that CsI:Tl and CsI(Tl,Ca) crystals have the cubic crystal structure with a dominant (110) plane. But CsI:Ca crystal has two dominant planes of (110) and (211). In addition, photoluminescence (PL) measurements were performed to investigate their optical properties: CsI:Ca and CsI(Tl,Ca) crystals emitted the blue light in a range of 420-450 nm wavelength with two dominant peaks but the orange light emission of 590-nm wavelength from CsI:Tl crystal. To evaluate the efficiency and energy resolution of radiation detection by coupling these CsI scintillators with a photomultiplier tube, the results reveal their different radiation performances due to the main difference in their optical properties about the light emission characteristics. In conclusion, the radiation performance of CsI:Ca scintillator has been still challenge to accomplish with the optimized growth condition and the suitable coupling devices.

Background: Overactivity of the bladder (OAB) affects 20% of people globally, causing urgency to void and incontinence of urine (UI)). OAB has a multi-factorial causation. Problematically current tests are invasive and provide limited information. Recent advances in NIRS technology now offer non-invasive evaluation of brain neuroexcitation and bladder hemodynamics/oxygenation related to micturition. We tested the hypothesis that brain and bladder parameters can be monitored simultaneously with patient-controlled quantification of bladder sensation, and that brain-mediated control impacts UI in OAB. Methods: A symptomatic patient (OAB) and asymptomatic control were monitored during spontaneous bladder filling to capacity with fNIRS of the anterior cortex and continuous wave NIRS of the bladder while using a validated patientcontrolled sensory meter. Changes in oxygenated, de-oxygenated and total hemoglobin in brain and bladder were recorded, and sensory events (bladder fullness/urgency to void) documented. Results: In the asymptomatic control fNIRS-derived neuroexcitation was evident when the bladder filled to capacity, increased at decision to void, was most intense during voiding, and waned thereafter. The OAB subject showed progressive increase in neuroexcitation from documenting a desire to void, to recording sensing urgency (imminent UI). At this point a distractor stimulus occurred (unexpected phone call), the sensation of urgency waned and an abrupt decrease in cortical oxyhemoglobin concentration was evident. Conclusion: Simultaneous brain fNIRS, bladder NIRS and sensation quantification is feasible and adds to OAB evaluation. fNIRS-derived neuroexcitation occurs in association with sensed voiding events. The attenuation of urgency/UI by a distractor stimulus implies brain-mediated mechanisms are integral to OAB.