This PDF file contains the front matter associated with SPIE Proceedings Volume 11371, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Electromagnetic constitutive properties can be extended by judiciously combining component materials to form a composite material. Provided that the granular dimensions of the composite material are much smaller than the electromagnetic wavelengths involved, the composite material may be regarded as a homogenized composite material (HCM). There are many ways in which the characteristics of HCMs can extend beyond those of the component materials; for examples, gain and loss, group speed, and weak nonlinearity may each be enhanced via homogenization. There even are many ways in which HCMs can exhibit characteristics that are not at all exhibited by their component materials; for examples, anisotropy and bianisotropy, Voigt-wave propagation, and negative phase velocity may be supported by HCMs whose component materials do not support these properties. The combination of active and dissipative component materials can yield HCMs that are neither wholly active nor wholly dissipative; such HCMs are can support plane-wave propagation, as well as surface-wave propagation, that is amplified for certain propagation directions but attenuated for other propagation directions.

We experimentally expanded the capabilities of optical sensing based on surface plasmon resonance in a prism- coupled configuration by incorporating artificial neural networks (ANNs). We fabricated a sensor chip comprising a metal thin film and a porous chiral sculptured thin film (CSTF) deposited successively on a glass substrate that can be affixed to the base of a triangular prism. When a fluid is brought in contact with the exposed face of the CSTF, the latter is infiltrated. As a result of infiltration, the traversal of light entering one slanted face of the prism and exiting the other slanted face of the prism is affected. We trained an ANN using measured reflectance data and found that the presence of the CSTF does not inhibit sensing performance. This finding clears the way for further research on using a single sensor chip for simultaneous multi-analyte sensing.

We experimentally demonstrate that graphene and graphene fluoride manifest different coefficients of sliding friction at the edges (graphene fluoride from 5.8×10^-3 to 4.9×10^-1; graphene from 8.2×10^-3 to 3.3×10^-1) of a sheet sample versus the interior (graphene fluoride from 5.1×10^-3 to 1.5×10^-1; graphene from 2.5×10^-2 to 2.3×10^-1) under ambient humidity conditions (~ 40-60%). Atomic force microscopy (AFM) was used to prove the friction coefficients show distinct directional dependence between graphene and graphene fluoride.

Recently, some work involving investigation of polarization states and Fresnel coefficients (FCs) at an achiral/chiral (ACC) interface indicated that depending on specific chiral bands and also the density (or phase index) of the two dielectrics, certain types of anomalous behavior would result. These anomalies included Brewster effects for s-polarized incident light, and total internal reflection (TIR) for propagation from lower to higher phase index. Analog time signals as well as 2-dimensional stationary images were propagated across the ACC boundary to determine the effect of chirality and parameters such as permittivity and permeability under dispersion.^1-3 Extensions to the case of two interfaces comprised of an ACC on the front end and a chiral/achiral (CAC) on the back will be considered in this work. We note that a slab resonator is amenable to analyses similar to a Fabry-Perot (FP) resonator. Analysis is carried out here for the chiral slab (say with thickness d) having both ACC and CAC boundaries; here multiple reflections and transmissions are expected. Matlab simulations are carried out by incorporating boundary conditions and deriving the effective transmitted and reflected fields relative to the slab. The results are examined for a thin chiral slab with thickness d (sandwiched between achiral surface and substrate layers) in the range 10-100 nm. The transmission characteristics (which are examined to study the resonance behavior of a typical FP etalon) are investigated as functions of wavelength or frequency in the thick and thin film limits, and results are compared from resonance, resolution and polarization perspectives.

The light absorption of wide bandgap semiconductors in contaminated water, allows them to promote redox chemical reactions. The foremost condition that ensures success is related to the spontaneous jump in the energy of the photogenerated charge carriers. The jump is from their conduction/valence band energy positions to the oxidizing/reducing levels of those contaminants, which produces the so-called heterogeneous photocatalytic water purification. In this work, ZnO thin films composed by nanostructured nanofibers and nanorods (NRs) were compared to address the drawbacks such as low absorption of the solar spectra, low active surface area, charge carrier’s recombination. These films were fabricated with various coupling and doped materials by electrospinning and hydrothermal techniques on fluorine-doped tin oxide (FTO) glass substrate. First, ZnO/TiO₂ films were fabricated using different zinc acetate-to-PVA ratios by an electrostatically modified electrospinning technique and then sintered at 600°C. Second, ZnO doped with nitrogen and silver (ZnO:N-Ag) nanorods films were vertically supported on undoped and N doped ZnO seed layers fabricated with different N:Zn ratio in the solution precursor by a wet chemical method.

Rooftop solar cells may become more acceptable if they are colored, e.g., red or bluish green, which requires that a certain part of the incoming solar spectrum be reflected. We implemented and optimized an optoelectronic model for Cu₂ZnSn(S_ξSe_1-ξ)₄ (CZTSSe) solar cells containing (i) a conventional 2200-nm-thick CZTSSe layer with homogeneous bandgap, or (ii) an ultrathin CZTSSe layer with optoelectronically optimized sinusoidally nonhomogeneous bandgap, or (iii) a CZTSSe layer with optoelectronically optimized linearly nonhomogeneous bandgap. Either complete or partial rejection of either red or bluish green photons was incorporated in the model. Calculations show that on average, the efficiency of a typical solar cell will be reduced by about 9% if 50% red photons are reflected or by about 13% if 50% blue-green photons are reflected. The efficiency reduction increases to about 18% if all red photons are reflected or about 26% if all blue-green photons are reflected.

Transitional metal oxides have generated considerable interest in electronics and other engineering applications over the last few decades. These materials show several orders of magnitude metal-insulator transition (MIT) when triggered by an external stimuli. In this paper, an MIT (Vanadium Dioxide (VO₂)) -based bimorph cantilever shows promising performance due to its large volumetric work density, ultrafast response, and reliability. This this work, we propose and simulate a cantilever actuated via VO₂ for a micro-contact switch. Our results show VO₂ based actuators show promising performance in terms of deflection, resonance frequency, and lifetime.

Recent developments in phase change materials have led to a new generation of electronic and photonic memory devices and thermally tunable devices. Vanadium dioxide (VO₂) and Germanium Antimoy Telluride (GST) are two of the most developed phase change materials. The focus of this work is on vanadium dioxide. Current methods of growing vanadium dioxide rely on reactive physical vapor deposition on heated and lattice-matched substrates. This is often a difficult deposition process with a very narrow process window. The high process tem- peratures, patterning and etching challenges, and the lattice-matching requirement severely limit the number of materials VO₂ can co-exist with. As a result, compared to other types of inorganic optical thin film materials, the development of practical devices exploiting VO₂ has been modest. In this paper, novel and simplified approaches to producing VO₂ thin films is discussed, especially in regards to creating multilayer optical structures, tunable optical filters, switchable wiregrid polarizers, and tunable Bragg reflectors. The growth and characterization of nanostructured VO₂ films are also discussed.

Vanadium dioxide (VO₂) is a well-known phase change material that shows a metal to insulator transition at temperatures near 68 °C. It has many potential applications in science and engineering. In this study, VO₂ thin film based planar spiral tunable inductors were designed and fabricated on a sapphire substrate. This approach can be a potential solution for reconfigurable RF/microwave wireless communication systems. According to the experimental results, fabricated inductors show a 43.4 % (from 2.19 nH to 1.24 nH) tuning range at 2 GHz when the VO₂ thin film layer undergoes the insulator-to-metal transition from room temperature to temperatures above the transition. This result confirms that the proposed inductor structure was fully functional with the successful inductance tuning capability.

ZnS thin film has wide applications in optoelectronics area, including photocatalysis and solar cells. The water bath is a popular ZnS thin film fabrication method, with merits of high efficiency, easy-operation, low cost, and uniform deposition. In this report, ZnSO₄7H₂O and thiourea were mixed in the water bath for reaction at a constant temperature with mechanical stirring. Thus-deposited ZnS thin film was then annealed in Ar. The impacts of different pH, different concentration, different water bath temperature, and different annealing temperature and time were studied to find the optimal condition. The optimal results were as follows: the mixture of 0.056mol/L thiourea and 0.0532mol/L ZnSO₄7H₂O in water was titrated to pH=10.7 by ammonia, followed by water bath reaction at 85°C, then annealed in Ar at 300°C for 1.5h. Thus fabricated ZnS thin film has the best surface flatness and film uniformity, with high optical transmittance.

In the present work, photocatalytic oxidation of Rhodamine B solutions were performed using a composite material prepared by titanium dioxide films deposited onto cobalt ferrite nanoparticles. Cobalt ferrite nanoparticles were prepared by coprecipitation of Co(II) and Fe(II) ions in basic medium, followed by a controlled oxidation process carried out by nitrate ions in basic medium in inert atmosphere at 95°C. The effect of 2 alcohols (ethanol and 2-propanol) as solvents in the deposition of TiO₂ films was studied as a function of CoFe₂O₄/TiO₂ mass ratios. Cobalt ferrite nanoparticles exhibited (36 ± 20) nm diameter with spheroidal shapes as confirmed by SEM studies. TiO₂ films deposited onto CoFe₂O₄ were thicker using ethanol as solvent according to SEM and TEM studies. Cobalt ferrite nanoparticles exhibit a weak oxidation behaviour since around 40% of Rhodamine is eliminated after 90 min of exposition. The 4 composite materials studied oxidize 100% of Rhodamine B after 60 min of reaction and kinetics results fitted a second order degradation reaction equation. As Rhodamine B solution pH was 5.83, faster reactions occur when composite materials develop low surface charge (PZC closer to 5.83) due to small surface charge repulsion. Materials prepared with CoFe₂O₄/TiO₂ ratios between 4 to 6 present higher kinetic constants which is confirmed by a faster Rhodamine B degradation

In this paper, GaAlAs/GaAs vacuum photodiodes are used to test the spectral response of different external electric fields, and the influence of external electric field on NEA GaAlAs/GaAs photocathode is analyzed. Based on the spectral response curves under different bias voltages, the external voltage increases and the corresponding spectral response sensitivity increases. As the bias voltage increases, the sensitivity of the spectral response increases slowly and gradually becomes saturated. This is mainly due to the fact that under the action of a strong field, the photoelectron obtains a sufficiently high energy to escape into the vacuum, resulting in a spectral response sensitivity tending to saturation.

Third-order nonlinear optical effects exhibited by Gold-Platinum nanoparticles in a Titanium Dioxide thin solid film were induced by a two-wave mixing configuration with digitally-modulated irradiance profiles. The nanomaterials were prepared by a sol-gel method, and a spinning coating technique was employed for the preparation of the samples in thin film form. We used a Nd:YAG laser system at 532 nm wavelength and 4 nanosecond for the exploration of the thirdorder optical nonlinearities. The characterization of the morphology and optical transmittance was carried out by transmission electronic microscopy and UV-vis spectroscopy studies; respectively. A round continuously variable nonlinear refractive index was proposed to generate twisted light by nanosecond pulses in the sample. The system was designed with a randomly distributed density of the nanoparticles. This technique can be considered an alternative for performing ultrafast all-optical instrumentation functions.

GaAs material has excellent photoelectric properties and is the most sensitive vacuum semiconductor material in the visible light band. GaAs photocathode has become the core component of low-light-level night vision device and been widely used in the field of low-light-level night vision. We systematically analyzed the structural characteristics of the low-light image intensifier and defined the boundary conditions of GaAs electron emission. It provided calculation basis for further analysis of the photoelectric effect of GaAs photocathode. We established GaAs crystal model on first-principle, calculated the energy band structure, and analyzed the mechanism of surface electrons escaping. After photon energy transferring to the electronic, electrons were excited and went out of its orbit, becoming free electrons and gaining initial kinetic energy. According to the experience, we assumed the collision energy loss rate after free electron diffusion process, and calculated number of electron collision in crystal model and displacement distance. Linear displacement distance is electron diffusion length. The initial kinetic energy of electrons excited by GaAs material depends on the energy of incident photons, as well as on the cathode's own temperature. We analyzed the relationship between the electron diffusion length of the material and the temperature. The electron emission characteristics of GaAs material were summarized, which provided technical support for the subsequent process research of this cathode material. GaAs low light image intensifier is made of the following parts: photocathode、 MCP、 screen and high voltage power. Using the elastic collision model, we calculated the energy of the photon transported to the electron transfer. Assuming the collision energy loss rate of electronic diffusion is 20% every time, free electrons crash until photon energy losses. The collision frequency and the moving distance are GaAs material properties. We analyzed the relationship between the temperature and electron diffusion length of GaAs in this paper.

This paper investigates the formation energy, atomic structure, electronic structure and optical properties of native point defects on n-GaN (0001) surface based on the first-principles of the density functional theory. The results find that the 𝑉_𝑁 is not easy to exist and the 𝑉_𝐺𝑎, 𝑁_𝐺𝑎 or 𝑁_𝑖 defects are most likely to appear on the n-type GaN surface. The substitutional defect 𝑁𝐺𝑎 , the interstitial defect 𝑁𝑖 and the single Ga vacancy cause the conduction band to drop and the Fermi level to enter the conduction band in a deeper extent. However, both the valence band and the conduction band move up at the same time with the increase of Ga vacancies, exhibiting p-type characteristics and reducing the n-type conductivity of the surface. The N-vacancy makes the conduction band shift upwards, which reduces the n-type metal conductivity. It is also found that the reduction of photon adsorption on the surface affects the photo-emission of the surface, which is detrimental to the optoelectronic devices with n-GaN and metal contacts. This study shows that 𝑉_𝐺𝑎, 𝑁_𝐺𝑎 and 𝑁_𝑖 native point defects all increase the doping difficulty of n-type GaN films and have a certain value for the fabrication of high-performance optoelectronic devices with n-GaN and metal contacts.