This PDF file contains the front matter associated with SPIE Proceedings Volume 11498 including the Title Page, Copyright Information, and Table of Contents.

Sunlight spectrum down-converting films absorb UV/blue sunlight and convert it in near infrared (NIR) radiation that generates electricity in conventional photovoltaic (PV) cells more efficiently. In this paper we report on down-convertors in the form of polymer nanocomposite films impregnated with nanoparticles of lanthanide phosphor NaYF₄:Yb³⁺, Tm³⁺ . This compound was synthesized using the wet method and ball-milled in nano-powder. The phosphor produced relatively intense NIR radiation if the region between 960 and 1100 nm with a quantum efficiency of ~5%. It was chemically stable and could be transferred in the polymer film using the open-air concurrent multi-beam multi-target pulsed laser deposition (CMBMT-PLD). Two beams from a Q-switched Nd:YAG laser at a wavelength of 1064 nm were used to ablate two targets. One PLD target was made of compressed nano-powder of the phosphor. The second target was made of polymer poly (methyl methacrylate) known as PMMA. The phosphor preserved its down-converting properties during the deposition and mixing with the polymer. The deposited PMMA+NaYF₄:Yb³⁺, Tm³⁺ nanocomposite films responded with uniform, mostly blue upconversion radiation to the testing illumination with a NIR laser diode at 980 nm. This proved that the phosphor nanoparticles were evenly distributed in the polymer matrix and preserved the optical properties of the PLD target. Post-deposition heating was shown to significantly improve uniformity of the nanocomposite films.

A great deal of research has been performed on refractive index n and extinction coefficient k due to varieties of applications in optical industries. The dispersion equation is described for the photons of varying energies and their interactions with materials since there is a strong correlation of n and k with wavelength. Measurements based on reflectance can be expensive and are very difficult due to compositional variations. We present a low-cost reflectance probe fiber optics designed in-house to determine the absorption coefficients and refractive index of solids. The solutions using a modified Beer-Lamberts Law and merging the concentration and extinction coefficient terms into an absorption coefficient, α, can be given by the equation I = I₀ exp (-α* d) where I is the transmitted intensity, I₀ is incident intensity and d is the thickness. We have experimented with several semiconductor compounds for this study.

Optical techniques offer a practical approach to characterize fluid dynamics due to the complicated nature of the mathematical equations that describe turbulent flows. However, experimental setups such as particle image velocimetry are often restricted to studies with steady flows moving through channels with clear walls to detect the signals from lasers using optical receivers and particles that reflect light. For non-isothermal unsteady flows in scraped surface crystallazers, the signal detecting process is not trivial due to the interference caused by the rotating shaft and the scraper blades that homogenize the solution in the mixing chamber. Also, the cooling jacket installed on the periphery of the agitator obstructs the field of view impeding the study of the interrogation region. The goal of this investigation was to determine the phase-transition temperature of a multi-phase unsteady flow in a scraped surface crystallizer using optical spectroscopy in the UV-VIS range. Temperature, pressure, and spectroscopy measurements were measured in-situ to characterize the mixture by its physical properties to obtain a correlation between the optical signatures before and after the glass-transition temperature. Results showed that optical absorbance successfully detected the physical variations in the phase- transition process of the unsteady flow.

Planck’s law predicts the distribution of radiation energy, color and intensity, emitted from a hot object at thermal equilibrium. The Law also sets the upper limit of radiation intensity, the blackbody limit. Recent experiments reveal that micro-structured tungsten can exhibit significant deviation from the blackbody spectrum. However, whether thermal radiation with weak non-equilibrium pumping can exceed the blackbody limit in the far field remains un-answered. Here, we use a tungsten photonic-crystal with a partially coated black surface to show that far-field thermal radiation can exceed the blackbody limit by > 8 times at 1.7 micrometer resonant wavelength. This finding is attributed to non-linear Bloch-waves and the excitation of dipole-active tungsten resonators throughout the photonic-crystal. This discovery could help create super-intense LED-like thermal light sources and even thermal emitters with laser-like input-output characteristics.

We have numerically investigated single quantum well (SQW) green InGaN-based light-emitting diode (LED) by simultaneously grading quantum well (QW), quantum barriers (QBs) and electron blocking layer (EBL). We compared the simulated results and found that our proposed structure has shown significant improvement in the hole injection. In addition, reduction of strong built-in electrostatic field in the proposed structure has improved the light output power by twice, reduced the efficiency droop by ~23% and improved the radiative recombination by ~46% in the proposed structure.

Today, one major obstacle for a broader impact and utilization of three-dimensional photonic-crystals (3D PC) is the lack of a scheme for low cost and large scale fabrication. In this work, we proposed a novel lithographic method to realize 3D PC that is inherently a low-cost and wafer-scale method. This method combines a 2D optical mask and off-axis double optical exposures to create 3D PCs having slanted rods and SP2 lattice symmetry. Three types of SP2 PC were successfully fabricated with a minimum feature size of d=1.5 micrometer over a large scale of 8x10 mm2, without any observable fabrication defects. The optical performances of the SP2 PCs were studied by FTIR reflectance measurements, indicating photonic band gap. Furthermore, this holographic method is ideal for creating a new class of slanted-rod based PC, such as topological PC in 3D, for new scientific discovery.

The primary objective of this effort is to demonstrate the efficacy of the Raman spectroscopy technique for detecting and evaluating the health of propellant stabilizers commonly used in missiles stored under a range of ambient conditions. Tincured silicone rubber doped with a commonly used propellant stabilizer N-methyl-4-nitroaniline (MNA) and ammonium nitrates used in explosives has been investigated using 532 nm and 785 nm wavelength laser Raman systems. The detected propellants’ Raman peak intensity ratios are used to analyze the results. Calibration curves with error bars are created using more than 30 data runs. The results indicate both systems are suitable to detect fractions of these chemicals as low as 0.2 percent within a few seconds of integration time. The calibration curves created for all the samples measured show a consistent linear increase to the ratio indicating the reliability of the measurements.

Many optical metrology applications require light that is both coherent and broadband. Supercontinuum (SC) spanning several wavelength octaves is an obvious candidate for such applications. Optical fibers are a natural platform for SC generation due to the long interaction length of light within the fiber which allows for broad SC which can ultimately be used as a tunable narrowband source. For tunability in the mid-IR regime, YAG fibers are an excellent candidate due to their high transparency, Kerr nonlinearity, and damage threshold. In our work, we study SC in undoped crystalline YAG fibers produced via laser-heated pedestal growth. We use femtosecond pulses to generate SC in fiber, pumping at several wavelengths ranging out to the mid-IR. Studying the power-dependence of SC generation, we use SC width and shape as indicators of mechanisms that generate SC at each pump wavelength.

In this study, we quantitatively simulate the thermal effect in the application of high-speed KTN beam deflectors. Dielectric heating can contribute to a substantial temperature increase in high-speed continuous KTN electro-optic (EO) beam deflection. The influence of dielectric heating in KTN is analyzed for different parameters, such as the beam deflection angle, geometric dimension, and the scanning frequency. The optimal structure that can minimize the thermal effect is explored.

Curie Temperature plays an important role in the applications of KTN crystals. However, every crystal is grown with a fixed Curie temperature. In this study, we present a method of manipulating the Curie temperature using strain. This could optimize the performance of our KTN deflectors and other applications.

We reported a new type of GaAs photoconductive semiconductor switch (PCSS) with nanostructured surface. Since the light could be entered not only from the top surface but also the side surface of the nanostructures, the effective penetration depth was significantly increased. This resulted in a longer lock-on time, which could be highly useful for a variety of applications that require longer lock-on time.

A method for writing programmable volume phase gratings into photorefractive materials using visible wavelengths in a transmission geometry, and then subsequently probing these gratings in a reflection geometry using infrared (IR) wavelengths to achieve specific angles of reflection of the probe beam is analyzed. The programmable features of these gratings include grating spacing and tilt, or K-vector magnitude and orientation. Relationships have been derived between the incidence angles of the writing beams and the corresponding reflection angles of the IR probe beam. More specifically, for a fixed angle of incidence of the probe beam, two unique writing beam angles can be found which generate a grating with the correct spacing and tilt to reflect and steer the probe beam through a wide field of desired angles.

The objective of this research is to determine the feasibility of a displacement sensor that can find applications in the fields of material characterization and structural health monitoring that is based on the Whispering Gallery Modes (WGMs) phenomenon. The proposed sensor configuration consists of a circular optical resonator embedded in a polymeric beam fixed at both ends. When the sensor is embedded within a beam, a deformation of the beam will result in a change of the morphology (deformation) of the resonator and consequently a shift in the wavelength of the optical modes. The optical modes produced in these types of resonators are extremely narrow showing a high optical quality factor and consequently leading to high-resolution sensors. An analysis based on the finite element method was performed to determine the behavior of this configuration. The purpose of this analysis is to determine the mechanical strain occurring along the circular resonator perimeter due to the application of the external linear displacement. Several parameters were investigated with regards to sensor sensitivity, including the resonator location within the beam and its diameter. Results show that with a resonator diameter of 3 mm located at the center in the horizontal direction and close to the top of the beam, a sensitivity of 0.05mm-1 can be obtained.

Stabilizing additives are added to solid rocket propellant systems to slow the break-down of energetic nitrogen-based compounds utilized in solid rocket propellants. Over time this results in a reduction of stabilizers and an increase of inert compounds, which decrease propellant performance. Raman spectroscopic techniques can detect changes in chemical concentrations due to the strong spectrum that these compounds demonstrate. In this study, two wavelengths, 532 nm, and 785nm are used to analyze the Raman spectra of samples to characterize the changes to compounds over time. Computational techniques are demonstrated to mitigate fluorescence and improve the signal-to-noise ratio of chemical peaks specific to stabilizer compounds. Fluorescence in the 532 nm Raman spectrum is examined as a method for characterizing propellant compounds, as 2-Nitrodiphenylamine (2-NDPA) traditionally has more fluorescence than Nmethyl- 4-nitroaniline (MNA), and the 532 nm Raman system traditionally detects more fluorescence than the 785 nm Raman system. Detection of the stabilizer, MNA, in concentrations ranging from 0.38% to 0.75% is demonstrated. Raman spectroscopy is shown to provide a rapid method for analyzing high and low concentrations of stabilizer compounds to determine the remaining viability of the propellant.

We experimentally demonstrate that dielectric metasurface can generate multi-channel vortex beams possessing different orbital angular momentums with arbitrarily engineered spin-orbit interactions. We propose a design principle of the proposed meta-atom that can modulate and switch spatial complex-amplitude information. Experimental results show that the proposed metasurface can generate multi-channel vortex beam arrays without interval noises, and it can make each vortex beam channel possess different spin-orbit conversion when the incident polarization is changed. These results provide a new opportunity to implement a novel vortex beam modulator, which can be applied for future development of quantum optics and optical communications.

We report on the design of an all-dielectric quasiperiodic grating coupler with rectangular Si ribs on a SiO₂ substrate. The structure consists of ten periods built by alternating Si ribs and air according to the S₄ step of the Fibonacci series, i.e., the period was made as ABAAB, where A (B) can be used as Si (air) or air (Si). The thicknesses of air and Si ribs were taken as 315 nm, with a total length for the unit cell of 1575 nm. The finite- difference time-domain (FDTD) technique was used to obtain the numerical data within the commercial software Lumerical FDTD. Multiple coupling efficiency peaks were observed owing to self-similarity effects. Furthermore, we show numerically that optimum wavelengths and coupling efficiency amplitudes can be tailored by varying the ribs’ etch-depth and the angle of incidence from the optical fiber, which makes the proposal relevant for efficient, broadband optoelectronic circuits.

Nowadays, different techniques are used for the manufacture of LPFG, some of them are the phase mask method or interferometric method, point by point method with ultraviolet light, electric arc method, mechanical method, chemical method, and CO₂ laser method. Favorable results have been obtained by applying the technique that uses CO₂-laser since it is not as complex as the methods mentioned above. In this work, the design and manufacture of cascade LPGs is done with a CNC CO₂-laser machine configured with 10 W laser power, velocity of 20% and 500 pulses per inch. The results of the transmission spectrum in the manufactured devices show significant changes in the transmission spectrum for the cascade gratings, When the number of gratings is greater a varied interference pattern is generated, and more resonance wavelength peaks appear. The proposed method is easy to implement and reduces the manufacturing time of the devices.

Modeling of InGaAs/AlGaAsSb avalanche photodiodes (APDs) is presented in this work. Based on a drift-diffusion theory, the APD dark- and photo-current and multiplication gain are simulated. The frequency response and bandwidth are also computed based on a derived formalism by following the carrier transit analyses. Modeling results of I-V curves, multiplication gain, breakdown voltage, excess noise factor, -3dB bandwidth and gain-bandwidth product are demonstrated. Some results are compared with the experimental report. The APD performance is further evaluated with respect to two of the key design factors, the multiplication and the absorption layer thickness, respectively.

We report on study of photonic device based on a new spectral Raman converter allowing conversion from incoherent double-scale pumping laser pulses into coherent solitons. The developed photonic device features saturable absorption in the fibre cavity of synchronously pumped Raman laser. Conditions are identified allowing conversion efficiency over 45%. The limitations and advantages of the proposed approach are demonstrated, and also the prospects of its implementation in an all-fibre configuration. Efficient conversion of noise-like laser pulses into coherent solitons through nonlinear Raman shift phenomena enables attractive prospects of application of localised noise-like wave objects capable of carrying relatively high energies.

We have computationally modeled a hollow-core photonic crystal fiber made up of methanol and silica for numerical study of linear effects, nonlinear effects and supercontinuum generation in the near-infrared wavelength region. We have obtained the dispersion in both normal and anomalous dispersion regimes with zero-dispersion wavelength at 1450 nm. The proposed fiber design possessed the nonlinear coefficient as 15.10 W^-1.km^-1 for the effective mode area 7.24 μm² at pump wavelength of 1.55 μm in the anomalous dispersion region. The proposed fiber design is able to generate the ultrabroadband supercontinuum spectrum 600-2400 nm in a 12 cm long fiber length using 12 kW input peak power. Such fibers are strong candidate for the applications in wavelength division multiplexing.

Here, we present the metasurface design to split the incident light into transmission and reflection spaces according to its polarization states, and at the same time, the distinct phase profiles are imparted to each space. For implementation of this scheme, the linearly birefringent meta-atom is utilized for distinct phases at different polarization states. Interleaving methods is also utilized for switching the transmission-type into reflection-type. Three samples are fabricated for experimental demonstration of proposed scheme, each of them is operating in linear, circular, and elliptical polarization pair. We expect the miniaturization of conventional system might be achieved using this scheme.

A one-shot fringe projection scheme with a 2D fringe pattern for tele-centric Fourier transform profilometry is presented. Even though the size of the inspected object is so small that the surface is not fully projected by one fringe, unwrapping can be performed without ambiguity.

A pulsed-encoding scheme for phase-shifting projected fringe profilometry is presented. The projected fringe patterns used to perform the phase-shifting technique can be used to identify the fringe orders directly. For the filed of view 300mm×300mm, systematic accuracy was approximately 600μm.

A one-shot method to describe the 3D shape of a rotating object is evaluated. A sinusoidal fringe pattern is illuminated on the rotating object. Fringes on the rotating object observed by the digital camera are blurred by the motion. The blurred fringes are analyzable to retrieve the profile of the rotating object.