This PDF file contains the front matter associated with SPIE Proceedings Volume 11547, including the Title Page, Copyright information, and Table of Contents.

Solution-processed light-emitting diodes (LEDs) are attractive for applications in low-cost, large-area lighting sources and displays. Organometal halide perovskites can be processed from solutions at low temperatures to form crystalline direct-bandgap semiconductors with intriguing optoelectronic properties, such as high photoluminescence yield, good charge mobility and excellent color purity. In this talk, I will present our effort to boost the efficiency of perovskite LEDs to a high level which is comparable to organic LEDs. More importantly, organic LEDs are difficult to maintain high efficiency at high current densities due to their excitonic nature and low charge mobilities. Low temperature solution-processed perovskite LEDs demonstrate remarkably high efficiency at high current densities, suggesting unique potential to achieve large size planar LEDs with high efficiency at high brightness.

We have proposed and experimentally demonstrated for the first time a Brillouin optical time-domain analyzer (BOTDA) assisted by Block-Matching and 3D filtering (BM3D) image denoising technique. BM3D uses the spatial-domain non-local principle to improve the denoising in the transform domain, thus it makes the degradation of measurement accuracy/experimental spatial resolution small when compared with non-local means (NLM) and wavelet denoising (WD). Moreover, we extend the BM3D image denoising to video denoising (Video-BM3D, VBM3D), in order to accurately measure the slowly varying temperature in long-distance BOTDA. VBM3D uses both the spatial and temporal correlations of the data for denoising, thus it can significantly reduce the noise and make the measured values close to the real temperature even if it is temporally changing. In this talk, we will review our work and discuss some future perspectives.

A smart cushion based on single-mode-fiber-multimode-fiber-single-mode-fiber (SMS) with core-offset splicing, which can simultaneously realize human vital signs monitoring and activity monitoring, is proposed and experimentally demonstrated. The SMS structure is sandwiched between a piece of fiberglass mesh and a polyvinyl chloride (PVC) layer and then embedded in a common home or office cushion, which is the component of the proposed cushion. When people sit on the cushion placed on a chair, micro-strain induced by human activity including respiration, heartbeat and body movement will change the output light intensity of the fiber structure. By signal processing algorithms including filtering, fast Fourier transform (FFT) and feature extraction, the respiration rate (RR) and heartbeat rate (HR) can be obtained and human activity state on the cushion including nobody state, movement state and normal state can be judged. Furthermore, the performances of two memory foam cushions with different thicknesses are compared and proven to be both available. Such a smart portable cushion can realize real-time, noninvasive and highly sensitive monitoring of vital signs and activities within the accuracy of one second, especially for the elderly in nursing homes and office workers.

A simple and effective interference fading suppression method for Φ-OTDR using optimal peak-seeking is proposed. This method can reconstruct the vibration signal with high fidelity under the premise of using only ordinary single-mode sensing fiber without changing the structure of the traditional Φ-OTDR system. Based on the data after interference suppression, we applied different machine learning models to recognize the invasive events category. The promising results show potential applications of Φ-OTDR equipment and future implementation with machine learning algorithms.

This paper proposes a simple and efficient approach for the estimation of carrier frequency offset (CFO) in coherent optical OFDM (CO-OFDM) systems. By zero-padding the first received OFDM symbol and performing discrete Fourier transform (DFT), the obtained spectrum will preserve the shape of the original transmitted spectrum, but with finer frequency intervals. Leveraging this feature and the matched filter concept, we can develop a CFO estimator that can achieve the optimum estimation performance whose estimation error variance can reach the Cramer-Rao lower bound (CRLB). However, to obtain the accurate the estimation of CFO, the zero-padding rate should be large enough and a search step is required in matched filtering. In order to reduce the implementation complexity of the proposed algorithm, we further simplify the cost function after matched filtering to an approximated cosine function. Given three test values, the CFO estimate can be directly calculated from the test functions, without complicated search. Simulation results verify the feasibility and simplicity of the proposed simplified CFO estimator.

Germanium photonic integrated circuits (PICs) have attracted great attention for developing mid-infrared nonlinear optics devices. However, it is challenging to develop a mode division multiplexing germanium PICs due to the strong mode dependence of the group velocity dispersion (GVD) in a germanium waveguide. We design a novel germanium convex waveguide, which has almost the same GVD curve for TE0 and TE1 modes. Flat GVD curves from -1450 ps/nm/km to -850 ps/nm/km are theoretically obtained within a spectral region from 2 µm to 2.5 µm. Our study is expected to open an avenue for exploring unprecedented MDM nonlinear applications.

This paper presents design, fabrication, and testing of a miniature thermo-pneumatic optofluidic lens. The 3D printing creates truly 3D structures that provide a new strategy for fabricating miniature optofluidic lenses with arbitrary microchannels. The 3D printing fabricates structures successfully solves the liquid leakage issue because microchannels can be embedded in the structure. Finite element simulations are introduced to assess the uniform temperature distribution. The focal lengths under different voltages are measured. The imaging properties are characterized. The results prove the lens can be used for fine tunable focal length applications by adjusting applied voltage.

A cavity-based two-stage XOR electro-optic directed logic scheme using a novel reflective-type microring resonator is proposed and simulated. The proposed design with only one microring resonator used has a smaller footprint, better robustness, and less workload for initialization than previous works.

Photonics systems in the ultra-violet to visible spectral regime are based on wide-bandgap materials and devices. The development of III-Nitride photonic and optoelectronic devices integrated on a monolithic semiconductor platform will enable radical advances in a wide range of applications, including: smart lighting, sensing, imaging, visible-light communications, chip-scale atomic systems (including optical clocks), quantum photonics and quantum communications. In this talk, I’ll present the design, fabrication, and characterization of the monolithic integrated laser diodes together with modulators, amplifiers, and detectors towards wide-bandgap photonic integrated circuits. The challenges and opportunities in seamlessly integrated III-nitride elements enabling photonic IC at the visible wavelength for many critical applications will be discussed.

Fiber-chip edge couplers are extensively used in integrated silicon photonic for the coupling of light between optical fibers and planar silicon waveguide circuits. We experimentally demonstrate several novel designs of edge couplers with eased fabrication process, i.e. fork shape and dual-trident SWG shape, based on Silicon-on-Insulator platform. These edge couplers show low coupling losses and possess large bandwidths simultaneously.

With the rapid development of photonic integrated circuit, waveguide-based electro-optic modulators are widely used in the fields of optical communication, optical signal processing and optical sensors. The Mach-Zehnder modulator is one of the most widely used device structures as a particular kind of optical switching element, which has the advantages of great accuracy and high sensitivity. We investigate two types of Mach-Zehnder modulators (using balanced and unbalanced interferometers) based on lithium niobate (LiNbO₃) through theoretical and numerical analysis. The transmission characteristics of the balanced Mach-Zehnder modulator are numerically analyzed while the electric field is applied across the waveguide in one of the arms (or the two arms) of the interferometer, and the transmission characteristics of the unbalanced Mach-Zehnder modulator with different length differences between the two waveguide arms are studied. Numerical calculation results show that the transmission of the waveguide in the Mach-Zehnder structure changes sinusoidally, with alternately switching between port 2 and port 4. The theoretical results in the present work can provide some guidance for developing the practical optical modulator devices.

Optoelectronic devices, such as photodetectors (PDs), integrated coherent receivers (ICRs) and microwave photonics integrated circuits (MPICs), are the fundamental and essential components to bridge the optical world and the electronic world and massively applied in emerging fields. Optoelectronic frequency responses, representing the optical-to-electrical conversion efficiency at different frequencies, are the primary and critical parameters for optoelectronic devices, which are essential and of great importance to be precisely measured in their development, manufacture and application. To achieve ultrahigh-resolution and multi-dimensional characterization, optoelectronic vector analyzers (OEVAs) utilizing photonics-based frequency conversion have been proposed and demonstrated. Benefitting from photonics-based frequency conversion and ultrahigh-resolution microwave technologies, the ultrahigh-resolution and broadband optoelectronic frequency responses are de-coupled from the joint frequency responses. Theoretically, sub-Hz frequency resolution together with hundred-GHz measurement range is potentially achievable. However, limited by the high-order sidebands and the high-order intermodulation sidebands stimulated by the nonlinear electro-optic conversion, the measurement accuracy is deteriorated and the dynamic range is considerably limited. Additionally, for the on-chip measurement, the relatively narrow working bandwidth of the on-chip electro-optic modulators places a restriction on the measurement range. Recently, great efforts have been devoted to eliminate the nonlinear errors, improve the dynamic range and extend the measurement range. In this paper, the influence of the high-order sidebands and high-order intermodulation sidebands on the measurement accuracy and the dynamic range of the proposed OEVA are comprehensively investigated. The techniques for implementing high-accurate and broadband OEVAs are reviewed and discussed.

The formation and manipulation of ultrashort pulses on chip would be of great interest to ultrafast optics and integrated photonics. One of the important issues is dispersion-assisted nonlinear interactions of broadband frequency components. In this paper, we show for the first time that a bilayer waveguide for quasi-TE mode produces a quite flat and saddleshaped dispersion profile. Different from previously reported TE-mode waveguides with flattened dispersion, the proposed waveguide exhibits a greatly simplified structure with no need for a high-aspect-ratio slot and has quite small group delay difference in a wide spectral range with four zero-dispersion wavelengths (ZDWs). For the first time we study supercontinuum generation in hybrid dispersion regime, in which the broadened spectrum covers a bandwidth with all ZDWs. It is found that one can obtain greatly improved spectral flatness in supercontinuum generation, with a power variation as small as 3 dB over a bandwidth of <500 nm. Moreover, the proposed waveguides are particularly suitable for low-distortion pulse propagation over a long distance, which is important for on-chip ultrashort pulse delivery.

By using a frosted glass plate and an infrared sensor card, we demonstrate a miniature imaging spectrometer design that covers a broad wavelength range from visible to infrared with high spectral resolution. The spectral contents of the incident probe beams are reconstructed by solving a series of matrix equations with a nonlinear optimization algorithm. The proposed imaging spectrometer offers significant advantages over current instruments that are based on Fourier transform and grating dispersion, in terms of size, resolution, spectral range, cost and reliability. The imaging spectrometer consists of five primary components for performing the functions of collimation, dispersion, modulation, detection, and calculation, respectively. Disordered small particles of the frosted glass in dispersion component reduce the fabrication complexity. An infrared sensor card in the conversion component broaden the operational spectral range of the system into visible and infrared bands. Since the CCD used in the detection component provides very large number of intensity measurements, one can reconstruct all spectra with high resolution.

Here, we theoretically study a novel multi-mode modulator based on a double-layer graphene-on-silicon waveguide. Our method is based on the exploration of tunable interaction between patterned graphene nanoribbons (GNs) on the surface of a silicon waveguide and zeroth transverse electric (TE0) and first transverse electric (TE1) modes in the waveguide. By adjusting the Fermi level of graphene sheets in the double-layer graphene-on-silicon waveguide, we could simultaneously and separately obtain about pi phase shifts of the TE0 and TE1 modes in the same waveguide. Our study is expected to open an avenue to develop high-density MDM photonics integrated circuits for tera-scale optical interconnects.

We investigate the response time of silicon-based thermo-optic switches under different device configurations. We design two tunable thermo-optic switches on a silicon-on-insulator (SOI) chip. One uses a waveguide embedded phase shifter based on direct heating due to electric current flow through waveguide. The other traditional switch structure has a metallic heater on top of the waveguide. Owing to direct current injection to heat the waveguide, which avoids the heat conduction from heater to waveguide, the switching time would reduce significantly. The experimental result shows that the direct heating device realizes a fast response time close to 1.5μs. As a comparison, the traditional heater-on-top device’s response time is over 10μs. That is to say, switching time of the direct-current-injection device is over ten times less. The insertion loss of both devices are reasonable. The fast heating device shows a potential for applications in the future optica interconnects.

We demonstrate a photonic crystal (PhC) waveguide modulator based on a Mach-Zehnder Interferometer (MZI) configuration on a silicon-on-insulator (SOI) substrate. A p-n junction is embedded in the PhC waveguide such that the carrier concentrations in the waveguide can be changed with applied voltage, which changes the refractive index of the silicon material forming the waveguide. Our PhC waveguide is designed to work at 1550 nm. The slow light effect in the photonic crystal waveguide can enhance light-matter interaction, which helps to achieve sufficient modulation in a short interaction length around 100 micron, which may also help reduce the power consumption. Modulation speed of 8.5Gb/s has been measured.

Reservoir Computing (RC) is a subset of Recurrent Neural Networks (RNN) and has emerged as a powerful method for large scale classification and prediction of temporal problems with a reduced training time. Silicon-Photonics architectures have enabled high speed hardware implementations of Reservoir Computing (RC). With a Delayed Feedback Reservoir (DFR) model, only one non-linear node can be used to perform RC. In literature, multi-layer photonic RC architectures have been proposed by stacking multiple reservoirs together. Such architectures have demonstrated improved performance over single reservoir networks. However, as we show in the paper, for each task, the performance improvements saturate with a different number of layers. Hence, a hardware accelerator with fixed number of reservoir layers is not optimal for all tasks. Moreover, the gain in performance also comes at the cost of increased power consumption. Therefore, in this paper we propose a new reconfigurable optoelectronic architecture for multi-layer RC. Our proposed architecture, is based on DFR model implemented by the use of Mach Zehnder Modulator (MZM) and on chip low loss delay lines for improved performance. It integrates photonic switches based on Micro Ring Resonators (MRR) to enable reconfigurability. The architecture enables layer selection and layer gating to select the number of layers required for a task. Selection of number of layers can optimize the architecture for a specific application, resulting in huge power savings, while maintaining the overall accuracy. Our experiments with NARMA task and analog speech recognition task show that by optimally configuring an up-to 4-layer architecture, power savings up to 40% can be achieved compared to state-of-the-art architectures while gaining up to 80% more accuracy. Our scalable architecture has an on-chip area overhead of 0.0184mm2 for a single delay line and MRR switch.

Space-chip coupling using silicon photonic grating coupler is of great significance for OPA-based LIDAR (Optical Phased Array, OPA), free-space data communication, and so on. However, Silicon-based grating couplers are commonly used for fiber-chip coupling and space-chip coupling is rarely mentioned. In order to obtain the optimal coupling effect, commercial three-dimensional Finite Difference Time-Domain (3D FDTD) software is employed to simulate the coupling process and analyze the characteristics of spatial light coupling. Because the spot size is in the order of micrometer, we first build a vector beam with three variables of numerical aperture, lens diameter and beam diameter for simulation. Afterwards, the incident location of the spatial light beam, the incident angle and the grating width are scanned to explore the influence of these parameters on coupling efficiency. We have found that the total coupling efficiency changes with grating width exponentially. That is, the total coupling efficiency firstly increases with the grating width, and does not change after reaching the maximum value. However, the coupling efficiency of the fundamental mode decreases gradually after reaching the maximum value. This indicates that higher-order modes are more likely to be excited when the width is greater than the optimized grating width. Besides, the coupling efficiency varies parabolically with the incident angle and location of the spatial light beam. There exists optimal incident angle and location on the parabola symmetry axis to get the maximum coupling efficiency. Furthermore, the best incident position is half of the beam diameter from the beginning of grating coupler.

In this study, nanostructured ZnO thin film photodetectors have been synthesized on transparent poly(ethylene terephthalate) (PET) and polyimide (PI) flexible substrates by radio frequency sputtering technology. Effect of growth temperature and oxygen flow rate on the crystallinity, optical transparency and light sensitivity of ZnO thin films were systematically investigated. XRD results reveal that ZnO thin films grown on both flexible substrates exhibit (002) c-plane oriented crystallinity. The crystalline quality of ZnO films greatly depends on the surface state of the flexible substrates, substrate temperature as well as oxygen concentration during growth. The average optical transparency is above 85% in the wavelength range of 300-1000 nm for these ZnO film samples on flexible substrates. Photoluminescence properties of ZnO films on both PET and PI substrates show no obvious band-edge emission, but high intensity of emission from defects. XPS results indicate that good stoichiometry composition transfer from the target to the films has been achieved by RF magnetron sputtering. Interdigital electrode (IDE) planar photodetector devices have been fabricated on PI substrates with Ag as the top electrode. The I-V characteristics of flexible ZnO PDs reveal good light detecting response with 3.8×10^-7 A photocurrents at light power current of 40A.

This work reports a graphene hyperbolic metamaterial hybrid plasmonic waveguides (GHMMHPW), and unlike traditional hybrid plasmonic waveguide (HPW), the GHMMHPW consists of a plasmonic cladding constructed by graphene hyperbolic metamaterial. Thanks to the particular structural arrangement, EM field can be localized and significantly enhanced in the low-index dielectric layer with nano-thickness. Thus, a superior performance is achieved. Meanwhile, electromagnetic parameters of graphene are tunable, and the mode properties also depend on the structural parameters, so the mode area and propagation distance can be optimized by adjusting these parameters flexibly. TM mode is supported in the GHMHPW, and improved performance is obtained. This study provides a novel and valuable reference for design of graphene plasmonic waveguides and prepares for the further development of micro-nano optics and integrated optoelectronic devices.

Hybrid plasmonic waveguides (HPWs) have attracted wide attention in recent years, because it makes a better compromise between the low loss of dielectric waveguide and the constraint capability of surface plasmonic waveguide. In this work, a hollow HPW with slat metal layer is analyzed to further reduce the loss and maintain constraint capability, then Bragg grating is designed and studied. By changing the waveguide width to further analyze the mode. The results show that normalized mode area is around 0.01, and propagation length (L_p) is up to 3500 μm, for TM polarized mode at operating wavelength of 1550 nm. For TE mode, L_p keeps millimeter level. Based on hollow HPW, Bragg grating is constructed by alternating the waveguides with different widths. Since the effective index of waveguide mode is quite sensitive to the change of the width and the trends of TM and TE modes are different from each other, Bragg gratings with different filtering characteristics and polarization properties can be designed by choosing combinations with different width. Simulations prove the validity of the design. HPW and Bragg structure proposed in this work would provide a reference for designing related photonic devices and have the potential applied value in the field of optical communication and integrated optics.

Sub-wavelength focusing of cylindrical vector beams has attracted much attention because of its special properties. On this basis, an all-dielectric concave grating lens with negative refractive index is proposed in this paper. Through discussing the influence of equivalent negative refractive index (n_eff) and preset focal length on the focusing properties, the parameters of the structure is optimized. The results show that when n_eff is -1, the focal size is the smallest. A smaller preset focal length results in a smaller the transverse focal size. Furthermore, the effect of higher order diffracted light is also studied. It is found that, sub-focusing can be suppressed effectively by removing the structural part that supports the higher order diffraction. Finally, not only the focusing property is improved, but also the structure is simplified. This work provides a flexible and feasible method for the design of negative-index lens, and offers a reference for manipulating the focus of CVBs. Therefore, it provides a scheme for focusing artificial microstructure.

Organic field-effect transistor (OFET) photonic memories have attracted significant attention due to their special memory mechanism and potential application, such as image capture and light information storage. Conventional OFET memories based on SiO₂ blocking dielectric layer usually need a high programming and erasing voltage, which is not conducive to the needs for future market applications. Here, the low-voltage OFET photonic memory is investigated by using spin-coated organic polymer as the blocking dielectric layer and blending film of CsPbBr₃ quantum dots (QDs) and polystyrene (PS) as the charge trapping layer, respectively. The thin poly(methyl methacrylate) (PMMA) film is used as the first blocking dielectric layer, and the ultrathin polyvinyl alcohol (PVA) film is used as secondary blocking dielectric layer on the top of PMMA. Due to the use of thin polymer blocking dielectric layers, the operating voltages of the photonic memory can be as low as 5 V. And the photo-generated carriers can be effectively trapped and released in photosensitive charge trapping layer during the photo-programming and electrical erasing operations. In addition, the memory characteristics of the photonic memory are comparable to that of traditional memories with SiO₂ blocking dielectric layer. Multi-level data storage can be obtained in the memory by applying different photo-programming conditions. The low-voltage OFET memory device also presents well retention and endurance. Hence, the low-voltage OFET photonic memory using solution-processed polymer blocking dielectric and photosensitive charge trapping layer shows great potential for the application in optoelectronic devices in terms of large-area and low cost.

Organic-inorganic metal halide perovskite material is an emerging semiconductor material that is widely used in functional devices such as solar cells and photodetectors. It has many advantages, low preparation cost, high light absorption coefficient, long carrier diffusion length, high carrier mobility, etc. However, due to the instability of perovskite, it is easy to decompose in the water and oxygen environment, which has become an obstacle to its development. In this paper, by adding polymethyl methacrylate to the anti-solvent to reduce the perovskite grain boundaries, improve directional growth and the quality of the film. The performance of the photodetector prepared by this method has been effectively improved, there is a significant photocurrent under illumination, and the stability has also been improved. This method provides a good candidate for the next generation of high-performance photodetectors.

In this paper, tapering process of glass capillary for fabrication of optical fiber components is studied. Tapering equipment with propane flame burner is built and tapering experiments of 1.25mm-diameter glass capillary using flame scanning technique are carried out. Additionally, FEM simulation on fluid dynamics of the capillary tapering process is performed using Comsol Multiphysics. With the simulation and the experiment results, relation of the tapering parameters and defects formation is analyzed, and the optimized tapering process is achieved.

Light-carrying orbital angular momentum (OAM) has recently drawn extensive attention from researchers due to its unique field distribution. As a result of the intrinsic orthogonality among OAM modes with different topological charge values, they can be used as a modal basis in the mode-division multiplexing (MDM) optical communications systems. For fiber-based optical systems, chromatic dispersion induces temporal optical pulse broadening, which seriously limits the rate of information transmission. Consequently, dispersion compensation fiber is promising for mitigating the chromatic dispersion of the complex beam in the optical fiber. We propose and design a novel germanium-doped silica ring fiber composed of two high refractive index ring regions that can support high order OAM modes with large negative dispersion. We numerically investigate the high-order OAM modes guiding property in the proposed fiber by using a full-vector finite-element mode (FEM). Since Ge-doped silica has similar physical properties to silica, they can be easily combined with a tunable mole fraction of GeO₂. Through varying the mole fraction of GeO2 and optimizing the structure parameter, we obtain a large negative dispersion of up to -99,685 ps/(nm·km) for OAM_11,1 mode at the wavelength of 1614.2 nm. Furthermore, we engineer the chromatic dispersion of some other OAM modes and investigate the effects of fiber parameters on the dispersion, which indicates that the fiber we design is able to support all the OAM_ℓ,1 modes (∣l∣≤11) with highly negative dispersion. The designed fiber with tailorable negative dispersion can be applied to compensate for positive dispersion in the OAM-based optical systems.

All-fibre mode-locked lasers represent a special class of lasers producing short radiation pulses and featuring maintenance-free operation, high wall-plug efficiency, and fairly high output parameter stability. Closed-off optical system of these lasers is convenient for users, but challenging for developers in the part of electronic control over the radiation parameters due to the peculiarities and limitations of the all-fibre technology. An overview will be presented, detailing the progress in means and methods of electronic control over the generation parameters of all-fibre ultrashort-pulsed lasers within recent years and showing the path to further development of electronic control technologies for such lasers.

The preparation of high-quality perovskite films with optimal morphologies is important for achieving high-performance perovskite photodetectors (PPDs). An effective strategy to optimize the morphologies is to add antisolvents during the spin-coating steps. In this work, an environment-friendly antisolvent ethyl acetate (EA) was employed to improve the quality of perovskite films, which can effectively regulate the formation of an intermediate phase staged in between a liquid precursor phase and a solid perovskite phase due to its moderate polarity, and further promote the homogeneous nucleation and crystal growth in the subsequent annealing process, thus leading to the formation of high-quality perovskite films and enhanced photodetector (PD) performance. As a result, the responsivity of the PPDs reached 0.85 A W^-1 under the illumination of 532 nm laser with the power density of 6.37 μW cm^-2 at bias voltage of -2 V. The corresponding detectivity reached 3.27 × 10¹¹ Jones, while the rise time and fall time are 256 ns and 370 ns, respectively. These results demonstrates that our developed solution-processed method with EA as antisolvent has remarkably advantages for the fabrication of high-performance PPDs and can provide a reference for the other similar research work.

Reported is an experimental study of a new approach to laser synthesis of arbitrary optical waveforms with nanosecond resolution. This approach relies on combination of a fast-recovery active medium (semiconductor optical amplifier, SOA) and a waveguide electro-optic switch which plays the role of a variable output coupler in a SOA-fibre laser. Programmable electronical control of output coupling allowed production of periodic and aperiodic arbitrary optical waveforms profiled with a nanosecond resolution at arbitrary repetition rates ranging from single shot to tens of MHz. The proposed method is distinguished by its simplicity, high efficiency, and relatively narrow output radiation spectrum.

A high dynamic range MOEMS accelerometer based on multi-order diffraction method is presented in this paper. The accelerometer consists of a frequency-stabilized laser source, a diffraction grating, and a mirror attached to a mass block with symmetric cantilever beams, to achieve a few ug resolution. The traditional interferometry only uses the ±1 order diffraction, the accelerometer can obtain high measurement accuracy but the measurement range remains only several mg. This paper introduces a new interferometric method combining ±1 and ±3 order diffraction, and the model of multi-order diffraction measurement is established. The higher order diffraction intensity is proportional to the lower order diffraction intensity, so the higher order diffraction light can be used to improve the dynamic range of the system. And positive and negative order diffraction difference can suppress the common mode noise at the same time. Theoretical analysis and experimental results show that the dynamic range of accelerometer is improved by 9 times under the condition that other conditions remain unchanged.

Wearable electronics are now moving towards transparent and stretchable promoting the synergetic development in transparent flexible energy storage devices. Typical supercapacitor electrodes suffer the stretchability limitation due to the material rigid and brittleness. Transparent stretchable electrodes are critical elements in the investigation of transparent and stretchable supercapacitors. Generally, the most widely used materials for TSEs are carbon nanotubes (CNTs), graphene, metal-nanowires, and metallic meshes. The homogeneous and designable metallic mesh attracted more attentions due to their high conductivity, thermal and air stability, easy management of optoelectrical properties and reproducibility. However, typical metallic mesh electrodes are usually substrate-supported with synthetic polymers, like polyethylene glycol terephthalate (PET), polyethylene naphthalate (PEN). The inherent properties of the substrate, such as greater thickness, lower optical transmittance, poor stretchability have appeared pronounced shortcomings. Here, we proposed a freestanding metal-mesh with serpentiform grid arrangement for its high transparency, super-flexibility and stretchability, and ultrathin thickness, which can be employed as high performance transparent stretchable supercapacitor current collectors. The solid supercapacitor assembled by the proposed stretchable and transparent electrode reveals a high transparency of 82% at the wavelength of 550 nm and large capacitance of 1.1 mF/cm². The superior device indicates an outstanding capacity retention up to 88% under 90% strain and sustained its electrochemical performance upto 67% even after 120% strain that meet the requirement in daily life condition. The serpentiform structured metallic mesh can be a strong candidate for future wearable electrochemical energy devices with superior transparency and stretchability.

Here we report a hybrid Bloch surface polariton waveguide by integrating a silicon nano-rib loaded periodic multilayer dielectric structure with a dielectric nanowire at telecommunication wavelength. The hybridization between the Bloch surface mode and dielectric mode is investigated by tuning the key structural parameters of the proposed waveguide. Owing to the existence of the silicon non-rib in close proximity to the dielectric nanowire, the characteristics of the Bloch surface mode can be strongly modified, enabling low-loss light guiding in conjunction with subwavelength mode confinement. Such hybrid configuration demonstrates significant superior light guiding properties over the conventional Bloch surface polaritons and nanowire polaritons, which may open possibilities of the implementation of a variety of high-performance integrated photonic components.

GaN-based multiple quantum well (MQW) light emitting diodes (LEDs) are promising to replace the conventional incandescent and fluorescent lamps due to recent improvements in material quality and device .Blue InGaN/GaN multiple quantum well light-emitting diodes with the conventional AlGaN and AlGaN-GaN-AlGaN (AGA) and many other novel structure electron blocking layer(EBL) are numerically investigated. When either AlGaN layer of a AGA EBL is inserted by a GaN layer leading to a multilayered structure, the simulation results show the Fermi level and energy gap of the EBL make a remarkable difference owing to the changed structure and the device with the new structure creates much higher output power as compared to those with conventional structure and AGA structure due to the enhancement of the electron confinement and improvement of the hole

A Lange coupler with a Ka-band (26.5~40 GHz) had been designed in a 0.15 μm GaAs MMIC technology. The coupler uses λ/4 wavelength lines as the coupling lines. The coupler was realized and measured by using 50 Ω resistors as terminations. The test results of the coupler within 26.5~40 GHz frequency range as follows: the coupling degree -3.2dB at the center frequency of 33GHz, insertion loss < 3.5 dB, return loss and isolation both less than -20 dB, amplitude imbalance less than 0.06 dB, phase imbalance less than 1°. The proposed Lange coupler has extremely wide application scenarios in MMIC circuits such as Ka-band power amplifiers, mixers, and phase shifters and so on.

A pivotal issue of the conventional optical fiber communications networks is to meet the explosively increasing requirement in data traffic. In order to meet this ever-increasing demand, there have been a lot of research and industrial development efforts to utilize the photon in various dimensions such as wavelength division multiplexing (WDM), space division multiplexing (SDM), mode division multiplexing (MDM) and so on. Fueled by emerging bandwidth-hungry applications, orbital angular momentum (OAM) modes and their multiplexing have recently gained much attention due to its special doughnut-shaped intensity distribution, as well as its unique helical phase wavefront with the theoretically infinite topological value. The OAM modes with different topological charge values are orthogonal to each other, which has provided a new degree of freedom in MDM. In this paper, we propose and design a Ge-doped air-core ring fiber, which can support numerous OAM modes. By varying the mole fraction of GeO2 and adjusting the structure parameter, including the air-core radius and the GeO2-doped ring width, we study the influence of the different fiber parameters on the total supported OAM mode number. The hollow silica fiber with a 50-μm air core and a 1.5-μm thickness of Gedoped ring is designed in simulation to support fiber eigenmodes up to HE_112,1 and EH_107,1. This provides 436 OAM modes at 1550 nm while maintaining radially single mode condition. Moreover, it can support more than 400 OAM modes from 1260 nm to 1625 nm, covering O, E, S, C, and L bands.

We demonstrate a simple multi-wavelength Brillouin-erbium fiber laser (MBEFL) with triple-Brillouin-frequency-shift spacing. The single-, double-, and triple-Brillouin-frequency spaced multilwavelentth generation of the MBEFL is investigated in this paper. The output of the MBEFL is optimized by adjusting the output power and wavelength of the Brillouin pump (BP) and the 980 nm pump power of the erbium-doped fiber amplifier (EDFA). In the experiments, when setting the BP power to 2.5 mw and the BP wavelength to 1530.33 nm and the 980 nm pump power of EDFA1 and EDFA2 to 286 mw, 330mw, respectively, up to 11 Brillouin stokes with triple-Brillouin-frequency-shift interval are generated. The output wavelength is tunable from 1529.55nm to 1561.01nm. The proposed multi-wavelength fiber laser has potential applications in the areas of space optical communication and optical communications and microwave signal source.

Ballistocardiography (BCG) is a non-invasive method to detect the heartbeat signal, which reflects the body recoils introduced by cardiac ejection. Compared with traditional heartbeat monitors, such as Electrocardiography (ECG), the BCG detection method can acquire heartbeat signals without any wearable devices, which is user-friendly. The device can be integrated into a cushion, which is convenient for users to monitor the heartbeat in long-term. In this paper, a BCG monitor based on the Mach-Zehnder interferometer (MZI) with a new phase modulation method is demonstrated. A low-cost and compact phase shifter is introduced to solve the problem of signal fading in the fiber-optic interferometer. The baseline drift produced from breath and noise can be removed by the phase modulation and accuracy BCG signal can be detected in the sitting position. Compared with existing BCG monitors, such as accelerometer-based and bathroom scales-based, our optical fiber interferometer-based BCG monitor has many merits including sensitivity, stable, and immune to electromagnetic interference (EMI). In conclusion, the BCG monitor based on optical fiber sensor has great potential in the long-term and real-time heartbeat monitoring.

Novel self‐organized nanograting structures with periodically assembled crystalline and amorphous phases are created in La₂O₃–Ta₂O–Nb₂O₅ glass by an ultrafast laser. Heat accumulation and the Ta₂O₅ content strongly contribute to the nanograting formation. The fabricated nanograting arrays exhibit a broadband polarization‐dependent attenuation effect in the near‐infrared region, which indicates the potential uses in the optical information processing at communication wavelengths.

Heart Rate Variability (HRV) analysis is an important tool for health monitoring. A non-invasive smart health monitoring system based on optical fiber interferometer can get HRV information from the Ballistocardiogram (BCG) signal. For some patients, the HRV can hardly be calculated due to the interferences from breath and other vibrations. In this research, we obtain a stable and high-sensitive BCG signal by a Mach-Zehnder interferometer (MZI) based sensor. In order to reduce the noise in signal, we introduce an advanced least mean squares (LMS) adaptive filter into the procedure. We use the signal processed by a bandpass filter as the ‘desired signal’ to deal with the raw data and obtain a preferable output for HRV calculation.

We propose a compact ultra-broadband silicon-on-insulator polarization rotator. The conversion area of the polarizer rotator is a stair-shaped waveguide, where the middle step is partially replaced by a sub-wavelength grating. The length of the conversion region of the polarization rotator is only 3.36 µm. For TM-TE and TE-TM working cases, the insertion loss is less than 0.9 dB, the polarization conversion efficiency reached 99%, and the polarization extinction ratio is greater than 20 dB, in an ultra-broad wavelength range of 1260 nm to 1740 nm, which covers O-, E-, S-, C-, L-, and Ubands.

In the era of big data, large scale classification and prediction problems pose new challenges that the traditional VonNeumann architecture struggles to address. This calls for implementation of new computational paradigms. Photonic reservoir computing is a promising paradigm for large-scale classification and prediction problems. Reservoir Computing (RC) has three layers: the input layer, reservoir layer and output layer. The reservoir layer is a random interconnected network of neurons that is independent of the task being performed using RC. This enables a particular reservoir to be used for multiple tasks, as only the output layer needs to be trained. The independent nature of reservoir layer provides an opportunity for parallel processing of multiple tasks at the same time. Unfortunately, the optoelectronic architectures for RC in literature do not exploit this capability. Therefore, in this paper, we propose a multi-layer opto-electronic hardware architecture for parallel RC. Our architecture employs time division multiplexing to perform jobs in parallel. The implementation of the reservoir is based on Delayed Feedback Reservoir (DFR) model. In our experiments, we study the performance of different configurations of the proposed architecture for NARMA task and analog speech recognition task. We show that our architecture can outperform some of the leading single layer architectures by up to 90% for NARMA task while performing analog speech recognition in parallel and closely matches the performance of leading multi-layer photonic RC architectures with an increased error of 8% due to parallel processing. The proposed high-speed architecture has a power consumption of ~50W for a 4-layer network.

Waveguide-coupled germanium (Ge) p-i-n photodetectors (PDs) have attracted much attention and have been investigated widely due to their high performance and enable on-chip integration. In this paper, we report on the fabrication and experimental demonstration of an integrated lateral waveguide p-i-n PD with additional Si doping. In order to achieve a high performance detector, we used a novel silicon substrate doping to improve the electric field intensity in the active region. It is demonstrated by experiment that the strategy using additional Si doping to decrease dark current and to increase the bandwidth is more favorable. Using the additional Si doped p-i-n junction, the waveguide coupled Ge-on-Si p-i-n PD shows a comprehensive performance improvement. With comparison to the conventional waveguide coupled Ge-on-Si p-i-n PD, such a PD, owns an about 60% improvement on the tested -3 dB opto-electrical cut-off frequency and shows the smaller dark current at voltage of -1 V. We obtained at a reverse voltage of 1V a dark current lower than 30 nA, a responsivity higher than 1.1 A/W at 1550 nm wavelength, and a -3 dB optoelectrical cut-off frequency over 25 GHz. Evidently, the waveguide coupled Ge-on-Si p-i-n PD with additional p-i-n junction is very effective to promote the performance of device, which is very promising to be applied in the further high power Ge-on-Si PD fabrication.

Due to the epsilon near zero (ENZ) effect, indium tin oxide (ITO) can be used in optical modulators and reduce the modulator’s size dramatically. The tunability of optical properties and the CMOS compatible capability make ITO more attractive. To study the properties of ITO thin films, several works have been done. Firstly, thin ITO thin films were obtained by magnetron sputtering with different oxygen flow rates ranging from 0 to 50sccm. Secondly, EDS was carried out to investigate the elements' content. It can be found that increasing oxygen flow rate increases the percentage of oxygen atom and Sn atom of ITO thin films. Thirdly, surface profiler was used to measure the stress value of the ITO thin films. We find that the tensile stress of ITO thin films tends to transform into compressive stress when the oxygen flow rate rises, which is worth considering in the design of devices. Fourthly, spectrometer and Hall effect measurement were applied to measure the normal incidence transmittance and electrical properties of the ITO thin films. Larger oxygen flow rate leads to the normal incidence transmittance of ITO thin films becoming larger. Hall effect measurement contributes to the conclusion that the carrier concentration of ITO thin films is able to range from 10¹⁹ to 10²¹ cm^-3, and that when the oxygen flow rate is not too large, as the environment oxygen increases, the carrier concentration decreases and the mobility increases. This research can contribute to the design of compact ITO based optical modulators so as to achieve a better performance, which can further the integration of optical modulators.

We propose a ring shaped sulfide based-chalcogenide photonic crystal fiber (PCF) that supports mono-radial pure vector modes (m=1). It consists of an As₂S₃ ring PCF composed from an annular core within a central air-hole and a ring of six missing air-holes. The proposed design is found to enforce wavelength independent “doughnut-shaped” mono-annular guided modes. This property is prominent since it opens the possibility to achieve the broadest and purest fiber SC vortex light supported by fiber eigenmodes of the fundamental radial order. By pumping the designed structure at 2.5 μm with 50 fs-5 nJ pulses, the generation of broadband coherent optical vortex supercontinuum in the mid-IR region extending from 1120 to 3650 nm at -20 dB level is obtained. This structure with such mid-IR transmission window provides large nonlinearities and shows to be very promising for SC generation and mode division multiplexing applications by means of OAM modes.

A pair of fiber links between NIM and Measurement and Test Center of Aerospace System Department (MTC) are realized by welding the dark fibers in the communication network. A new device with integrated fiber optics and electrics is used to transfer the standard frequency signal via the fiber links. Here we show the main modifications of this device comparing to the old version. By short connecting the end of the fiber links at MTC, a double length fiber link is used to the test the transfer stability of the device. With an 83-days standard frequency transfer measurement, the Allan deviations show the transfer stability is better than 1E-14@1s and 7E-18@1day. This result indicates the new designed device is suit for the hydrogen masers comparison between NIM and MTC.