This PDF file contains the front matter associated with SPIE Proceedings Volume 10755, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

We report on the polymer nanocomposite films doped with the nanoparticles of rare-earth (RE)-doped fluoride phosphor NaYF₄:Yb³⁺,Er³⁺ (molar proportion: a = 3% of Er³⁺, b = 1 to 5% of Er³⁺, and [100% - (a + b)] of Y³⁺) for efficient luminescent solar concentrators (LSCs). The films are deposited using the concurrent multi-beam multi-target pulsed laser deposition of the inorganic target material and matrix assisted pulsed laser evaporation of the polymer (MBMTPLD/MAPLE). Polymer poly(methyl methacrylate) known as PMMA was evaporated and deposited on a glass plate from its solution in chlorobenzene frozen in liquid nitrogen with the fundamental harmonic (1064 nm) of a Q-switched Nd:YAG laser concurrently with the inorganic phosphor target ablated with the 2-nd harmonic (532 nm) of the same laser. The sun light is absorbed by the phosphor nanoparticles embedded in the 250-nm thick polymer film and converted in near-infrared (NIR) radiation via the mechanism of downconversion (quantum cutting). The NIR radiation propagates via the glass plate as a light guide and is converted in electric power with photovoltaic cells attached to the edges of the plate. The advantage of the proposed polymer nanocomposite LSCs is a broad absorption spectrum covering a significant portion of the solar radiation spectrum, high spectral conversion efficiency, and low reabsorption due to minimal overlap between the absorption and emission spectra (large Stokes shift). The power concentration factor of the polymer nanocomposite LSC is expected to be of the order of 10.

A series of Er³⁺/Yb³⁺ co-doped fluorophosphate glasses with varying YbF₃ concentration were prepared by a high temperature melt quenching technique. The effect of sensitization on various spectroscopic properties of Er³⁺-doped fluorophosphate glasses was investigated. Using the Judd-Ofelt theory, the intensity parameters (Ω_λ, λ = 2, 4 and 6) were evaluated from the absorption spectra of glasses. Absorption and emission cross-sections were determined by using the McCumber theory. The dependence of Er³⁺ ions near infrared emission (1.54 μm) on the Yb³⁺ concentration was investigated. The upconversion studies were also carried out at room temperature and low temperatures. The wider bandwidth (78 nm), larger emission cross-section (9.86 x 10^-21 cm²) and longer fluorescence lifetime (12.37 ms) were noticed for the ⁴I_13/2 → ⁴I_15/2 transition of ABS3Er4Yb glass. The temperature sensing behavior of the ABS3Er5Yb glass was studied by using the fluorescence intensity ratio technique in the temperature range from 100 K to 280 K. The sensitivity and temperature of the maximum sensitivity were found to be of the order of 15 x 10⁻⁴ K⁻¹ and 271 K, respectively. The results suggested that the present glass composition has possibilities for optical applications.

We suggest to use photoinduced photogalvanic electrical discharges produced by the ferroelectric Fe: LiNbO3 crystals for effective water splitting for production of oxygen and hydrogen by pulsed electrolysis. Electrical self-pulsations may be initiated by CW illumination with incoherent light, including Sun-light. Electrical pulses ( in microsecond range and with kV amplitude) are generated by the bulk photovoltaic (also called photogalvanic) effect. For separation of oxygen and hydrogen gases we apply magnetic field in Hall-effect configuration, with crossed electric and magnetic fields . Adding H-field to the traditional electrolysis scheme in the Hall effect geometry may give new opportunity for control of oxygen and hydrogen production. In this geometry water will be rotated that helps separation of oxygen and hydrogen. Rotation of water explained by the action of Lorentz force in geometry with cylindrical electrodes (cylindrical electrolyzer) that move oxygen and hydrogen bubbles with different signs of charges in the same directions. Hydrodynamic modeling suggest that converse effect: generation of electrical current, when water is rotating in the magnetic field, is possible to realize.

To minimize the influence of the refractive index mismatch between transparent conductive layer (e.g. Indium Tin Oxide (ITO)) and glass substrate on the light outcoupling efficiency (LOE) of organic light emitting diode (OLED), in this paper, we present a blue OLED with high LOE by incorporating a layer of tilted nanotube array as an internal light extraction structure in an optimal location. In comparison with conventional planar OLED, the LOE can be increased from 10.9 to 55.3%. The increase in LOE is mainly due to the strong disruption of waveguided mode. The tilted structure can be potentially used to develop high efficiency OLEDs.

Photonic Crystal Fibers have proved to be an efficient medium for propagation of electromagnetic radiation especially in the Terahertz regime. Located between the infra-red and microwave region, the Terahertz frequency range lies within 0.1 to 1 Terahertz. We report a design of a graduating ring rectangular-core Photonic Crystal Fiber, having background material as Cyclic-Olefin Copolymer (COC), with extremely low confinement loss of 4.9399 × 10⁻⁷ dB/cm and material loss of 0.2 cm⁻¹ at 0.22 mm pitch value. Due to the very low loss values, such a structure of the Photonic Crystal Fiber can be used for efficient low-loss data communication.

Conventional materials engineering approaches for polycrystalline ceramic gain media rely on optically isotropic crystals with high equilibrium solubility of luminescent rare-earth (RE) ions. Crystallographic optical symmetry is traditionally relied upon to avoid scattering losses caused by refractive index mismatch at grain boundaries in randomly oriented anisotropic crystals and high-equilibrium RE-solubility is needed to produce sufficient photoluminescence (PL) for amplification and oscillation. These requirements exclude materials such as polycrystalline sapphire/alumina that have significantly superior thermo-mechanical properties (Rs~19,500Wm^-1), because it possesses 1) uxiaxial optical properties that at large grain sizes, result in significant grain boundary scattering, and 2) a very low (~10^-3%) RE equilibrium solubility that prohibits suitable PL. I present new materials engineering approaches operating far from thermodynamic equilibrium to produce a bulk Nd:Al₂O₃ medium with optical gain suitable for amplification/lasing. The key insight relies on tailoring the crystallite size to the other important length scales-wavelength of light and interatomic dopant distances and show that fine crystallite sizes result in sufficiently low optical losses and over-equilibrium levels of optically active RE-ions, the combination of which results in gain. The emission bandwidth is broad, ~13THz, a new record for Nd³⁺ transitions, enabling tuning from ~1050nm-1100nm and/or ultra-short pulses in a host with superior thermal-mechanical figure of merit. Laser grade Nd:Al₂O₃ opens a pathway for lasers with revolutionary performance.

We analyze laser pulse propagation in a semiconductor with nonlinear absorption depending on free electron concentration and a concentration of ionized donors. Under certain conditions this interaction is accompanied by a resonator-less optical bistability appearance. It is an attractive modern problem because of developing the all-optical methods for data treatment. In contrast to many investigations made early we take into account a longitudinal diffraction of the optical beam. It means that we consider optical beam diffraction along coordinate of its propagation. This results in the presence of the optical radiation reflection from spatio-temporal contrast structure induced by the laser pulse. As a result, we observe a propagation of the fast light corresponding to wave reflected from a semiconductor as well as unmoving part of the pulse placed near the semiconductor face. The reflection of laser pulse from the boundary of high absorption domain is demonstrated. This phenomenon takes place due to presence of high gradient of optical properties of a medium.

In this work we present application of opto-numerical methodology for improvement of functional parameters of polymer optical bridges working as splices between two optical fibers. Optical bridges are formed by means of photopolymerization with light emerging from one fiber and coupled into the second axially-aligned fiber, therefore creating a stable mechanical connection. To fully determine and improve properties of this kind of microstructures, experimental methods are combined with numerical modeling. The parameters describing functionality of the polymer optical bridges are optical losses (insertion and return), which determine the usability of those elements as optical fiber splices. These parameters are the function of such features as: refractive index distribution, geometry of the microstructure and the wavelength of propagating light. To analyze the relation of those features on the functional parameters of the studied microstructures, the experimental results are compared to the ones obtained with simulations. Numerical modeling of aforementioned optical bridges is performed by means of the finite-difference time-domain method, which allows analysis of the electromagnetic field propagating through the microstructure. Experimental methods consist of optical diffraction tomography, which is used in order to obtain full three-dimensional refractive index distribution of optical bridge, and measurements of optical losses. Implementation of the proposed methodology in iterative procedure allows to optimize the fabrication procedure in order to produce efficient and reliable optical splices with desired functional parameters – insertion loss at the level 0.2 dB and return loss below -60 dB.

In cable industry, structural health monitoring is becoming more and more important. Of special relevance is the damage detection in cables which supply large excavation equipment like bucket wheel excavators in opencast mining. Here, damage localization is often still carried out manually. With a usual cable length of a few kilometers, this method is inefficient and can lead to unnecessary revenue losses caused by long repair and machine downtime. Because of their electromagnetic immunity, their functionality over long transmission distances, their resistance to difficult environmental conditions, and their comparatively easy integrability, fiberoptic sensors are particularly suitable for detecting damages in this application. Therefore, in this paper, a novel spatially resolving and inexpensive damage detection system based on fiberoptic reflectors is presented. With a physical vapor deposition method, an increased reflectance of the coated single mode fiber ends was achieved. Due to the special integration position of the sensors in the braiding structure of a cable, damage in the jacket area can be detected. Via measurements of the reflected signal intensities, the position of the damage can be resolved over long distances. Furthermore, the sensor arrangement engages only slightly in the manufacturing process of the cable braiding and the cable. The ability of the presented measurement system to perform damage detection independent of the regular power transmission of the cable offers an advantage over standard cable conductor based electrical damage detection techniques.

The demand for high-bandwidth communication networks and higher frequency signal processing has motivated the development of RF photonics, where RF signals are up-converted to the optical domain to be processed by photonic techniques. Over the last two decades, great strides have been made in this field; however, high-resolution processing is a bottleneck preventing low guardbands in data transmission thereby limiting data-transmission capacity. This is due to the lack of narrowband and single-passband photonic processors that can process RF information with high-resolution in the optical domain. Stimulated Brillouin scattering (SBS) is a nonlinear optical process between two counter-propagating optical waves and an acoustic wave, which can alleviate this bottleneck due to its narrow resolution of as low as 3 MHz, while allowing for frequency tuning in excess of 30 GHz. However, SBS is known to suffer from high spontaneously-generated noise, as well as saturation effects that limit the dynamic range of the RF system. In this work, we demonstrate RF bandpass filtering using the SBS loss response created through the anti-Stokes interaction using a phase-modulated analog photonic link and low optical pump powers. This enables an enhancement of the signal to noise ratio of an RF tone by up to 8 dB and the linearity by up to 3 dB, when compared to using the Stokes component associated with SBS gain. This technique is compatible with analog photonic link optimization techniques, and paves the way for the realization of compact and low-power SBS-based filters based on a photonic chip that can be implemented in practical systems.

We present the first heater integrated nanostructured optical fiber of 200 μm diameter to realize a high-sensitivity and reusable fiber-optic gas sensor. In our guided mode resonance-enabled fiber-optic gas sensor, resonance shifts upon the adsorption of the analytes on the graphene oxide (GO) coated sensor surface. For repeated use of this sensor, a regeneration of the sensor surface is required by a complete desorption of the analyte molecules from the GO layer. In our presented design, this has been achieved by the integration of a controllable heater at the fiber tip. The heater was fabricated by embedding a helical thin nichrome wire wrapped along a cylindrical rod into a precursor solution of polydimethylsiloxane, and subsequently removing the rod from the cured elastomer and leaving the helical wire inside the elastomer. Thus, a cylindrical cavity of length 16 mm and diameter 4 mm surrounded by the helical wire was formed that then contains the fiber-tip sensor. For the ethylene gas analyte, we demonstrated the reversibility of the heater integrated fiber-tip sensor, with a tunable recovery time. Owing to the rapid heat transfer from the helical wire to the encased fiber-tip sensor, the heater integrated fiber-tip sensor responds to heating in only about 2.5 min. The high resonance sensitivity of the nanopatterned fiber-tip to its surrounding refractive index, in conjunction with excellent repeatability through integrated heating for surface regeneration, enables a practical fiber-tip based remote sensing.

Newtonian mechanics assumes the essence of light is particle, Electrodynamics regards the essence of light is wave, while Quantum mechanics thinks the light is something that has the nature of wave-particle duality. According to Gödel incompleteness theorem, these theories could not be complete even if they were self-consistent. In fact, modern physics has not been able to give a unified explanation of the fundamental interactions in nature. In this article, a general field theory is developed based on an assumption that photon is an entity particle. In contrast with point particle, entity particle is an object that has both mass and volume. Photon is entity particle and is ubiquitous in the universe. Starting from the particle distribution in 3-dimensional Euclidean space, a set of partial differential equations for particle field is derived with the tools of vector analysis and field theory. This article analyzes the property of particle field, and explains the relationship of different fields and interactions. Particle field can be divided into three categories: density field, potential field and action field. Density field includes mass density and momentum density, which satisfy the laws of conservation. Potential field includes mass potential and momentum potential, which are the spatially correlated statistics of density field. Action field includes gradient field, divergence field and curl field, which are the first-order space change rate of the potential field. It is shown that the mass potential is equivalent to the gravitational potential and the electric potential. The momentum potential is equivalent to the magnetic potential. Gravitational field and electric field belong to gradient field, motional dissipation belongs to divergence field, and magnetic field belongs to curl field. The gradient of divergence field is the wave equation whose solution contains the light wave and the gravitational wave. The results clearly show that field is a statistical effect of a huge number of particles. Entity photon is the medium or ether that transmits light wave and gravitational wave, and the mass of photons is the so-called dark matter in the universe.

A resonant wavelength detection system based on a gradient grating period guided-mode resonance (GGP-GMR) filter and a linear charge-coupled device is demonstrated. The GGP-GMR used in this work consists of a subwavelength grating structure with a grating period varying from 250–550 nm in increments of 2 nm. We successfully demonstrate that by using this system, we can monitor the shift in a biosensor’s dip wavelength caused by different sucrose concentrations. This technology has the potential to replace a bulky and expensive spectrometer used in most optical biosensor systems. Given its compactness, the system can be integrated with lab-on-a-chip systems for numerous biosensing applications.

The photonic crystals possess complex dispersion relation and the unusual dispersion leads to negative refraction. Based on negative refraction, three main physical phenomena, negative Goos–Hänchen displacement, inverse Doppler effect and abnormal Cherenkov radiation have been proposed. In this work, two abnormal physical phenomena are discussed. Firstly, the negative Goos–Hänchen shift displacement is simulated by using common FDTD method. The negative displacement is measured experimentally at the wavelength of 10.6 μm. Secondly, a novel phenomenon, the dual Doppler effect, in the simultaneous occurrence of both normal and inverse Doppler effect in one moving two-dimensional wedge-type photonic crystal with negative index is investigated by using spatial Fourier Transformation. This phenomenon is also simulated by an improved FDTD method. The results have potential applications in precision measurement, cloaking, sensor, radar deception and so on.

This study reported an all-fiber sensor based on an asymmetric structured microfiber modal interferometer. The proposed sensor was easily created on a single-mode-fiber(SMF) by means of electric arc discharge technique. The dips of the reflection spectrum caused by the cladding modes interfering with the core mode shifted when the temperature and the refractive index changed. Due to its compact configuration and cost-effective, such new device would have promising applications in sensing fields.

We report numerical analysis of the four graded indium compositions and their influence on the optoelectronic performance is reported. We propose a wedge-shaped indium grading with a better optoelectronic performance in comparison to the other three structures. The proposed structure has significantly improved internal quantum efficiency, light output power and radiative recombination.

The need for high power, physically robust infrared laser systems that are capable of functioning in extreme environments has fueled the need to look for alternatives to the current state-of-the-art glass fiber sources. In particular, improvements to thermal management and a low stimulated Brillion scattering threshold are needed to increase the average output power of glass fiber systems. Rare earth (RE) doped single crystal fiber lasers have been proposed as a potential alternative with improved thermal management issues and a decreased SBS threshold. Recently, high-quality single crystal RE doped YAG fibers grown using laser heated pedestal growth (LHPG) have become commercially available [1]. LHPG has the potential to deliver flexible fiber sources that have the advantages of both single crystals and fibers, at a fraction of the cost of current bulk growth methods. Although LHPG single crystal fibers have demonstrated lasing, significant optimization of the fiber parameters must be done before they are suitable replacements for state-of-the-art laser fibers. In this study, the lasing properties of LHPG single crystal RE doped YAG fibers will be investigated to determine the efficiencies, loss mechanisms, and optimal doping levels for maximum output. The results will be discussed and possible design improvements will be proposed for future work. [1] G. Maxwell et al., Proc. SPIE 8733, 1-8 2013.

An Fe²⁺-doped ZnSe saturable absorber mirror (SAM) were fabricated by electron beam evaporation technique. In the Fe²⁺-doped ZnSe SAM, Fe²⁺ was doped into the bragg stack, in which Fe²⁺:ZnSe served as both saturable absorber and high reflection layer. By using the Fe²⁺-doped ZnSe SAM in the fiber laser, which operating at 2.78 μm, stable Qswitched pulse was obtained and the repetition rate was from 78.79 kHz to 162.32 kHz. The recorded maximum average output of 865 mW was achieved.

In this paper, we quantitatively simulate the thermal effect of charging and discharging process of high speed KTN beam deflector. The influence of thermal effect on beam quality is quantitatively analyzed. The method of reducing the thermal effect via a multi-layer design is also explored.

A sensitive Raman spectroscopy technique is used for detection and possible quantification of the propellant stabilizer, nmethyl nitroaniline (MNA), in solid rocket propellants used in multiple domestic missile systems. Over time, the energetic ingredients of the propellant will degrade and react with the stabilizer, causing issues with the propellant useful safe life. Currently, there are no non-destructive analytical techniques for which MNA can be detected in solid rocket fuel inside a missile. Therefore, after a certain amount of time, missiles in inventory must be disassembled and tested for reliability and safety. This methodology is labor intensive, costly, and time consuming so a less intrusive approach is warranted to determine a missile useful safe life. Raman spectroscopy provides a possible solution to this problem, where a small fiber optic probe line may be inserted into the rocket motor of the missiles, which can be tested within seconds without the need for dismantling the missiles. A 785 nm portable Raman analyzer is used for all measurements reported in this paper with integration times ranging from 10 to 60 s. It is found that Raman sensing is a viable option for detection of MNA in solid rocket fuels.

The electric field or stress applied to a solid material can change its polarization or dimensions, thereby altering its properties and causing a piezoelectric effect. This effect can positively or negatively impact your material depending on the sought after application. In this paper, we present a quantitative COMSOL simulation on the influence of the piezoelectric effect on the performance of high speed KTN deflectors. This includes examining the following aspects: piezoelectric induced mechanical stress and refractive index modulation. Furthermore, methods of minimizing the negative impact of piezoelectric effect, such as soft clamping, are explored in order to optimize the performance of electro-optical deflectors.

In this paper, we reported a method to fabricate 2D hexagonal lattice Holographic Polymer-dispersed Liquid Crystal (HPDLC) grating with variable period by using cylindrical waves interfere with plane waves. In order to separate polymer from liquid crystal syrup, a 532nm laser with an exposure intensity of 16mw/cm² was used to expose. Two steps exposure techniques was adopted in the experiment with the expose time of 2s and 60s in the separate steps to form the 2D gratings. In the second exposure step, the sample was rotated by anti-clockwise 60° to form 2D hexagonal lattice structure within H-PDLC grating. The theoretical equations for describing the variable period grating is analyzed. What’s more, the diffraction efficiency and other characteristics of this grating is also studied experimentally. The experimental result shows that fabricated grating with the continuously changing periods varying from 1.679 micrometer to 2.051 micrometer within the radius of 6 mm circle sample area, which is corresponded to the theoretical simulation quite well. The first-order diffraction efficiency was tested around18.3%. The intensity of transmission beam increased from 15.6% to 73% when applied with the driving voltage from zero to the maximum of 90 V. This 2D grating has the potential application in diffractive optics such as a tunable multi-wavelength organic laser device etc.

This paper, originally published on 4 September 2018, was withdrawn per author request.

We numerically report a design of a highly nonlinear spiral-shaped photonic crystal fiber (PCF) in Ga₈Sb₃₂S₆₀ chalcogenide glass for nonlinear applications in mid-infrared region. We have tailored the structural parameters to obtain all-normal and nearly zero flat-top dispersion profile. A flat-top dispersion curve is obtained with a negative dispersion value of -98.63 ps.nm^-1 km^-1 . This structure possesses a very high nonlinear coefficient of 49190 W^-1 km ^-1 with effective mode area of the propagating fundamental mode as 0.833 μm2 at a pump wavelength of 1.9 μm. This highly nonlinear spiral-shaped PCF is suitable for the generation of an ultra-broadband supercontinuum spectrum in mid-IR domain. Various nonlinear applications of supercontinuum generation are pump-probe spectroscopy, nonlinear microscopy, metrology, frequency combs generation and optical coherence tomography.

A one-shot technique for profile measurements is presented. A two-dimensional deinge-encoded pattern is used to illuminate the inspected object and a monochromatic camera is employed to observe the deformed fringes at another view angle. The 2D fringe-encoded pattern provides additional information to identify the fringe order. Even though the surface color or reflectivity varies rapidly with positions, it distinguishes the fringe order very well.

A fringe projection method based on the phase-shifting technique for 3D shape measurements is presented. Phase extraction is performed by the phase-shifting technique, while unwrapping is discerned by the phase-encoded patterns. There is no need to take additional projections for phase unwrapping. The fringe patterns used for phase extraction can be directly utilized for unwrapping. Experiments show that absolute phases could be obtained with high reliability.

A full-field method using fringe patterns to identify the profile of a specular surface is presented. A virtual image of the fringe pattern is formed by the specular surface. The specular surface deforms the image of fringe pattern. Thus, phase of the deformed fringes can be utilized to retrieve the profile of the inspected surface.

A scanning fringe projection technique is presented to retrieve the 3D shape of an object with large depth discontinuities. A 1D sinusoidal pattern is employed as the projected pattern. With a reliable image processing algorithm, noises and errors are efficiently detected and reduced.

Pyroelectric effect is one of the phenomena that can convert dissipated thermal energy into useful electric energy. Pyroelectric energy conversion from Lithium Tantalum Oxide (LiTaO3) crystal is evaluated by dynamic optical Chynoweth method. To improve conversion efficiency, an efficient a.c./d.c. converter for the harvester and variable load is developed. Analysis and experimental research were conducted over a range of resistive load and chopping frequencies in order to optimize the energy harvesting process by implementing impedance matching for maximum power transfer. In this experiment, direct current (d.c.) at nA level and voltage (d.c.) of 100 mV level are measured for several frequency and loaded conditions. After comparing the results at different conditions, best output is identified for chopping frequency at around 4Hz for 20 MΩ resistive load, by providing cyclic temperature fluctuations of around 1.25 K/s on a single crystal lithium tantalum oxide (LiTaO3). The generated pyroelectric current is converted from a.c. to d.c. by a voltage doubler. Chopping frequency range between 2Hz-6Hz and load range between 10MΩ-40MΩ are found important for optimum power generation from a 0.5mm thick LiTaO3 sample with a surface area of 19.64 cm². The potential for utilizing pyroelectric crystal in self-powered ultra-low power electronic devices are being further explored.

In this paper, we have reported a new design and demonstrated the analytical study of the hollow core negative curvature fibers (HCNCFs). Hollow core negative curvature fibers (HCNCF) is a kind of hollow core leaky mode optical fiber, which is defined by the negative curvature of the core boundary. These typical optical fibers consist of an arrangement of capillaries tightly packed over the hollow core. Due to their unique arrangement it creates a boundary of negative curvature with respect to the core of the fiber. As compared to with photonic bandgap fiber this specially designed hollow core negative curvature fiber shows low loss, wide bandwidth and maximum power confined in the core. Numerical simulations were performed using COMSOL software to study the properties of HCNCFs. In the simulations, it was found and reported that the capillary thickness is the most important factor determining the attenuation of HCNCFs. These features make the negative curvature fiber highly advantageous with tremendous potential applications in optical communication and sensor applications.