This PDF file contains the front matter associated with SPIE Proceedings Volume 10344, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

We experimentally demonstrate photocurrent generation from a titanium nitride thin film forming an interface to a zinc oxide thin film by the illumination of visible light up to 800 nm in wavelength. The photocurrent is attributed to hot electrons excited in titanium nitride whose excitation is not limited by the bandgap of zinc oxide. Our result paves the way to use titanium nitride instead of metals for phototectors and solar photocatalysis.

We propose to use femtosecond laser direct writing technique to realise dielectric optical elements from photo-resist materials for the generation of structured light from purely spin-orbital conversion transformations. This is illustrated by the fabrication and characterisation of spin-orbital optical angular momentum couplers generating optical vortices of topological charge from 1 to 20. The elements achieved using this techniques also were demonstrated its capabilities to working in the whole visible range with efficiency up to 85%. We also firstly demonstrated the abilities to combine the dynamic phase and geometric phase using the 3D fabrication capability of laser direct writing to create elements that generate different topological charges of optical vortices simultaneously with the shared aperture.

We report on the formation of periodic structures on the (100) crystalline silicon surface after irradiation with a low number of 1055 nm, 850 fs laser pulses, in high vacuum conditions. Our analysis focuses on the nascent stage of surface structures formation. We employ a wide variety of microscopy techniques to retrieve the morphological, optical and structural properties of generated structures. Sample topography is measured by means of an Atomic Force Microscope. Sample structural phase is revealed by performing a Raman micro-analysis through a scanning confocal optical microscope, while confocal and wide-field reflection images of the sample surface are also registered. Our analyses clearly show, besides the topographic ripples, the creation of grating structures of near-wavelength period consisting of alternating amorphous and crystalline periodic lines, with almost no material removal. The gratings originate from defects acting as scattering centers and generating energy modulation patters propagating along the direction of laser polarization.

In this paper, we present results authors published initially on the white light emission with broad band (330-465 nm) excitation of the specially prepared nano-phosphor: Eu³⁺: ZnS which is capped with sodium methyl carboxylate and on pure red-light emission from the nano-phosphor when capped with alpha methyl acrylic acid and prepared in a different method. Then we discuss possible methods of future improvement of the white light emission from the nano-phosphor. We then present the cost effective and energy efficient method of obtaining highest quality natural white light sources using such nano-phosphor and blue or near UV blue light emitting diodes. The latter discussion includes the driving circuit for the white LED and powering the LED by concentrated solar photovoltaics for both lighting and waste heat energy storage for completely clean energy natural white lighting sources.

Electronic states in a GaAs conical quantum dot (QD) are theoretically investigated within the framework of the geometric adiabatic approximation both in the strong and weak quantum confinement regimes. For the lower levels of the spectrum, the localization of the electron in the vicinity of the QD center-of-gravity is proved. The QD conical symmetry leads to the appearance of an atypical linear term in the effective confining potential. The influence of a uniform electric field on the system is also considered, and both the quantum-confined and pseudo- Stark effects are discussed. The possibility of the quasi-continuous spectrum implementation in the system is revealed in the presence of an electric field. For the weak quantum confinement regime, the motion of the exciton's center-of-gravity is quantized, which leads to the appearance of additional Coulomb sub-levels.

Optical transmissivity and reflectivity of one dimensional array of metallic nanowires embedded in transparent dielectric is characterized. i employ wave optics simulation to analyze the optical field distribution in both the dielectric and the nanowires. The results indicate that the transmissivity and reflectivity depend on the polarization states of the incident light. The metallic nanowires matrix transmit in-plane polarization but block light out at of-plane polarization.

In this study, we have demonstrated a facile chemical route to prepare CdSe QDs with white light emission, and the performance of white CdSe-based white light emitting diode (WLED) is also exploded. An organic oleic acid (OA) is used to form Cd-OA complex first and hexadecylamine (HDA) and 1-octadecene (ODE) is used as surfactants. Meanwhile, by varying the reaction time from 1 s to 60 min, CdSe QDs with white light can be obtained. The result shows that the luminescence spectra compose two obvious emission peaks and entire visible light from 400 to 700 nm, when the reaction time less than 10 min. The wide emission wavelength combine two particle sizes of CdSe, magic and normal, and the magic-CdSe has band-edge and surface-state emission, while normal size only possess band-edge emission. The TEM characterization shows that the two different sizes with diameter of 1.5 nm and 2.7 nm for magic and normal size CdSe QDs can be obtained when the reaction time is 4 min. We can find that the magic size of CdSe is produced when the reaction time is less than 3 min. In the time ranges from 3 to 10 min, two sizes of CdSe QDs are formed, and with QY from 20 to 60 %. Prolong the reaction time to 60 min, only normal size of CdSe QD can be observed due to the Ostwald repining, and its QYs is 8 %. Based on the results we can conclude that the two emission peaks are generated from the coexistence of magic size and normal size CdSe to form the white light QDs, and the QY and emission wavelength of CdSe QDs can be increased with prolonging reaction time. The sample reacts for 2 (QY 30 %), 4 (QY 32 %) and 60 min (QY 8 %) are choosing to mixes with transparent acrylic-based UV curable resin for WLED fabrication. The Commission International d’Eclairage (CIE) chromaticity, color rendering index (CRI), and luminous efficacy for magic, mix, and normal size CdSe are (0.49, 0.44), 81, 1.5 lm/W, (0.35, 0.30), 86, 1.9 lm/W, and (0.39, 0.25), 40, 0.3 lm/W, respectively.

All-dielectric nanoparticles have attained a lot of attention owing to the lesser loss and better quality than their metallic counterparts. As a result, they perceive applications in the field of nanoantennas, photovoltaics and nanolasers. In the dielectric nanoparticles, the electric and magnetic dipoles are created in dielectric nanoparticles when they interact with the light of a particular frequency. Kerker’s type scattering is obtained where electric and magnetic dipoles interfere. In our design, Silicon cylindrical nanoparticles having radius of 70 nm and length 120 nm have been considered. The propagation of light is taken along the length of the cylinder. The scattering cross section has been obtained and plotted with respect to the wavelength. At the peaks of scattering spectra, electric and magnetic dipoles are created at the wavelengths of 510 nm and 600 nm, respectively. Both dipoles interfere at the wavelengths of 550 nm and 645 nm. At these wavelengths, far field scattering pattern has been calculated. At the wavelength 645 nm, forward scattering takes place because electric and magnetic dipoles are in phase at this wavelength. Further, directivity is enhanced by taking the planar array of the nanoparticles. It has been observed that directivity increases by increasing the size of the array. Also, there is an increase in the directivity by increasing the gap between the nanoparticles. This enhancement of directivity can lead to the design of all dielectric cylindrical nanoantennas.

Multilayered germanium nanocrystals embedded in silica (SiO₂) matrices are fabricated by using the radio frequency magnetron co-sputtering technique. Transmission electron microscopy shows germanium (Ge) nanocrystals are confined in the (Ge+SiO₂) layers in the silica thin films. Linear optical absorption coefficients at different wavelengths and the energy gap of the films are calculated based on absorbance measurement data. Photoluminescence emission property is also characterized. Using the open aperture z-scan technique, we have also measured nonlinear absorption and computed the imaginary part of third-order optical susceptibility of these samples.

Nanostructured organosilicon luminophores (NOLs) consist of two types of covalently bonded via silicon atoms organic luminophores with efficient Forster resonance energy transfer (FRET) between them. Such molecular structure allows NOLs to combine the best properties of organic luminophores and inorganic quantum dots: high absorption cross-section and photoluminescence quantum yield, large pseudo-Stokes shift, fast luminescence decay time, good solubility and processability. Thin films of NOLs or their composites with optical plastics are transparent, which leads to efficient and fast conversion of UV into visible light in different types of photodetectors and other optoelectronic devices. This paper briefly reviews recent advances in the application of NOLs as wavelength shifters (WLS) in various types of elementary particles photodetectors: liquid xenon detectors with PMT and silicon photomultipliers, plastic scintillators and scintillating fibers, pure CsI scintillators.

Transparent conductive oxide materials have shown unique optical properties, such as negative refraction, hyperbolic dispersion, and epsilon-near-zero dispersion. In particular, aluminum-doped zinc oxide (Al:ZnO) has shown the most promising results over traditionally used noble metals. Pulsed layer deposition is a popular technique due to its fast and controlled growth rate, as well as the stoichiometric target-to-substrate material transfer. But, since it uses large and inhomogeneous kinetic energy, samples could be prone to macro- and microscopic defects. In this work, we investigate multilayered samples of Al:ZnO/ZnO grown by pulsed laser deposition with the goal of developing a low-loss metamaterial with hyperbolic dispersion. Different fabrication conditions, such as Al:ZnO/ZnO ratio, the thickness of an individual layer, different substrates, and deposition temperatures, were investigated. Results of the ellipsometry analysis, based on fitting spectroscopy data using the Berreman formalism, show that the hyperbolic dispersion transition (Re ε_∥>0, Re ε_⊥< 0) is achieved at λ_c=1868 nm wavelength (Im (ε_⊥)~0.03) for samples with 1:4 Al:ZnO/ZnO deposition ratio. The fitted dielectric functions for samples with various parameters show that a lower deposition temperature leads to a shorter transition wavelength.

Two-dimensional transition metal dichalcogenides (TMDs), which are atomically thin semiconductors consisting of transition metals M-(Mo, W, Sn, etc.) covalently bonded to chalcogens X-(S, Se, Te), have recently been the focus of extensive research activity due to their remarkable properties and especially emission properties. Nevertheless, such remarkable properties can strongly be altered once the atomically thin layer is deposited on a support. In this study, we report on the integration of freestanding TMDs. Monolayer (1-L) MoS2, WS2, and WSe2 as representative TMDs are transferred on ZnO nanorods (NRs), used here as nanostructured substrates. The photoluminescence (PL) spectra of 1-L TMDs on NRs show a giant PL intensity enhancement, compared with those of 1-L TMDs on SiO2. The strong increases in Raman and PL intensities, along with the characteristic peak shifts, confirm the absence of stress in the TMDs on NRs. In depth analysis of the PL emission also reveals that the ratio between the exciton and trion peak intensity is almost not modified after transfer. The latter shows that the effect of charge transfer between the 1-L TMDs and ZnO NRs is here negligible. Furthermore, confocal PL and Raman spectroscopy reveal a fairly consistent distribution of PL and Raman intensities. These observations are in agreement with a very limited points contact between the support and the 1-L TMDs. The entire process reported here is scalable and may pave the way for the development of very efficient ultrathin optoelectronics.

Many researchers have produced various results for the mechanism of the metal-insulator transition (MIT) of VO₂. This seems to be because of the influence of various VO_x phases in the sample thin-film. VO_x has many phases, and VO₂ is in only a small window in the VO_x phase diagram. In this work, VO₂ thin films on Al₂O₃ substrates were prepared by a pulsed laser deposition method, and their I-V properties were measured over a temperature range from 50 K to 300 K. In the thin-films, not only the VO₂ phase, but also at least two other VO_x phases were present, including V₂O₃ and V₅O₉. For electrically triggered MIT, a space charge limit current (SCLC) appeared at high voltages while ohmic current appeared at low voltages, and MIT occurred when the space charge density became greater than the critical carrier density, nc. This is a current-driven device, basically, because MIT occurs after the charge carrier density, which is injected from the electrode becomes higher than nc. The switching time, which is the time for the whole sample to transition from insulator to metal because of bias application, depends on the charge carrier mobility in the insulator state. The switching speed of VO₂ due to electrical triggering must be slower than that of optical triggering because the mobility of the charge carrier in the insulating state is only 0.5 cm²/V•s. For a simple two terminal model, the switching speed is proportional to the square of the length between the two electrodes and the mobility of the charge carrier, and inversely proportional to the voltage. Therefore, a proper switching speed can be designed for one’s use if the appropriate material and dimension of the device are used.

Quantum confined semiconductor materials in colloidal form have drawn great attention in scientific communities due to the size-tunability, which controls their optical properties. PbS quantum dots (QDs) are exciting candidates for quantum optics, particularly due to the control of the QD sizes during the synthetic process enabling the realization of precisely tunable emission properties in the near-infrared region. Differently sized pairs of PbS QDs were deposited onto glass substrates to form thin films using supercritical CO₂ (sc-CO₂) deposition and solvent deposition methods (SDM). The fluorescence and photoluminescence (PL) spectra obtained from these closely packed films prepared by the sc-CO₂ method reveal effective Förster resonance energy transfer (FRET) between two different sized dots, while the films composed of three different QD sizes show an even more effective FRET from the smallest to the largest ones. Energy transfer can be observed more directly by temporally resolved PL decay of mixed dots. By means of transient lifetime measurements, a mixed PbS film with 3.1 and 4.7 nm QDs was studied for FRET by time correlated single photon counting. The PL peak of the 3.1 nm QDs is quenched with respect to the emission of the 4.7 nm QDs and decays faster, and the best fit for the lifetime (decay constant)^-1 is a biexponential decay mode. The long wavelength decay (4.7 nm QDs) is best fit by a mono-exponential equation. More theoretical and experimental work is required for a thorough understanding of the radiative lifetimes of PbS QDs in mixed QD systems.

Optical properties of cyanine dye molecules incorporated in nanotubes of natural chrysotile asbestos are studied. The absorption and fluorescence spectra of dye in asbestos have the similar shapes as in the ethanol solution, apart from small blue shift of the maxima. The Stokes shift in asbestos is smaller than in the ethanol solution. The fluorescence decay times of the dyes in asbestos nanotubes are found to be larger than that in the case of thin films of the same dyes formed on the transparent dielectric supports. This observation is rationalized in terms of the stereoisomerization hindrance in the excited electronic state of dye molecules. At the same time linear dichroism and fluorescence anisotropy observed in the experiment indicate that the embedded dye molecules are well-isolated monomer oriented predominantly along asbestos nanotubes.

Upconversion luminescence, visible emission on infra red (IR) excitation was achieved in a biocompatible material, fluoroapatite. Fluoroapatite crystals are well known biomaterials, which is a component of tooth enamel. Also it can be considered as an excellent host material for lanthanide doping since the ionic radii of lanthanide is similar to that of calcium ion(Ca²⁺) hence successful incorporation of dopants within the lattice is possible. Erbium (Er), Ytterbium (Yb) co-doped fluorapatite (FAp) nanoparticles were prepared by precipitation method. The particles show intense visible emission when excited with 980 nm laser. Since upconversion luminescence is a multiphoton process the excitation power dependence on emission will give number of photons involved in the emission of single photon. Excitation power dependence studies show that two photons are involved in the emission of single photons. The value of slope was different for different emission peak because of the difference in intermediate energy level involved. The crystal structure and morphology of the particle were determined using X-ray diffractometer (XRD) and field emission scanning electron microscope (FESEM). These particles with surface functionalisation can be used for live cell imaging.