This PDF file contains the front matter associated with SPIE Proceedings Volume 13140, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

There is a continuous demand for more sensitive detectors of ultraviolet (UV) radiation. Popular silicon-based optoelectronic photodetectors perform poorly in UV spectrum. Integration of photoluminescent (PL) media capable of down-converting UV into visible (VIS) light (more suitable for silicon) with the photodetectors improve their UV sensitivity. We considered two such media: polymer nanocomposites impregnated with the nanoparticles (NPs) of perovskite CsPbBr₃ and phosphor NaEuF₄. We proposed to enhance the photoluminescence (PL) of the spectrum down-converting nanocomposites by embedding the nanoparticles (NPs) of high-entropy metal alloys (HEA) and using the surface plasmon polariton (SPP) resonance effect in such NPs. We proposed to fabricate HEA NPs and embed them in the nanocomposite using the patented concurrent multi-beam multi-target pulsed laser deposition (CMBMT-PLD) method. A two-step approach for making the nanocomposites impregnated with HEA NPs includes making HEA films using CMBMT-PLD followed by laser ablation of the films, formation of the HEA NPs during such ablation, and embedding them into a polymer matrix. By simulating the latter process with the ablation of the deposited HEA films in water the extension of the SPP resonance to the long-wave UV region (450 nm) has been demonstrated. A manifold improvement of the PL intensity of the nanocomposites due to SPP resonance in the embedded HEA NPs is expected. The obtained results will have an impact on the science and applications of short-wavelength sensors.

We have developed a new method for optical limiting using a system of coupled optical cavities with a PTsymmetric spectrum of reflectionless modes. The optical limiting occurs when the PT symmetry is broken due to the thermo-optic effect in one of the cavities. In our experiment, we used a two-cavity resonator with PT-symmetric spectral degeneracy of reflectionless modes created from alternating layers of cryolite and ZnS. We demonstrated optical limiting by measuring a single 532-nm 6-ns laser pulse. Our experimental results are supported by thermo-optical simulations, which provide deeper insight into the dynamics of the limiting process. Compared to existing limiter designs, our optical limiter offers a customizable limiting threshold, high damage threshold, nanosecond activation time, and broadband laser protection. Additionally, we have shown a method to achieve an even broader transmission spectral bandwidth by implementing this concept in a four-cavity resonator with greater coupling strength using similar materials.

This work presents the fabrication and experimental demonstration of heterogeneously integrated photodetectors using monolayer WS₂, aimed at advancing ultra-thin optoelectronic devices. By employing silicon nitride wafers with SiN/SiO₂ layers, precise device patterning was achieved through electron beam lithography and dry etching, followed by the integration of WS₂ flakes using a wet etching technique. The study focused on the device's broadband transmission properties, observing a significant shift in the exciton absorption wavelength (~10 nm) due to strain introduced during the integration process. This shift highlights the potential for manipulating optical properties through strain engineering. The devices exhibited high spectral responsivities at the WS₂ exciton wavelength, demonstrating their efficacy in the visible spectrum. These findings pave the way for future on-chip photonic devices operating at visible wavelengths, with promising applications in strainoptronics and other advanced optoelectronic systems.

A volume holographic material based on the ethylene glycol phenyl ethyl acrylate (EGPEA) monomers with various initiator concentrations in the host matrix PMMA is synthesized. For a polymer with a thickness of 460μm and an illuminating power density of 12.55mW/cm², a Bragg grating with the diffraction efficiency of 75% can be formed in 18 seconds.

In this paper, we report how to use femtosecond laser illumination to inscribe micro/nano structures, particularly the permanent periodic refractive index change/modulation in functional crystalline materials, such as lithium niobate and Ti: sapphire crystals. First, we introduce the motivations to create micro/nano structures in functional crystalline materials, which include the enhancement of light and material interaction, leading to new functionalities such as a spectrally tunable electro-optic device. Second, we discuss the physical mechanism of femtosecond laser illumination induced permanent refractive index change. The extreme high light intensity at the focusing spot of femtosecond laser beam can induce a rapid melting/re-solidification process in the functional crystalline materials, consequentially generating a permanent refractive index change in these materials via Kovacs effect. Third, we provide a detailed description of the experimental setup and procedure used to inscribe permanent periodic refractive index modulated patterns in functional crystals. We use the direct femtosecond laser writing method due to its simplicity and versability. Fourth, we discuss the experimental results confirming that we can indeed inscribe permanent periodic refractive index change in functional electro-optic lithium niobate crystals and the Ti: sapphire lasing medium. Finally, we will conduct and report experimentations to confirm the applications of micro/nanostructured functional crystalline materials in highly compact and fast-speed tuning lasers and spectral filters in future.

In this paper, we report the growth of ytterbium-doped lithium niobate (Yb:LiNbO₃) crystalline fibers by laser heated pedestal growth (LHPG) method. In the growth, first, a Yb:LiNbO₃ bulk crystal is grown by melting the Yb:LiNbO₃ powder in a platinum (Pt) crucible at 1300 °C. Second, a Yb:LiNbO₃ bulk crystal is cut/lapped/polished in a rectangularly shaped bar, which can serve as the feed rod of LHPG. Finally, a Yb:LiNbO₃ fiber is drawn using the LHPG method, in which the Yb:LiNbO₃ bar is served as the feed rod, and a pure LiNbO₃ crystal bar is served as the seed rod. The major properties of the Yb:LiNbO₃ fiber are evaluated, including (1) identifying the composition of the fiber by energy dispersive spectroscopy (EDS), (2) determining the crystalline structure by X-ray diffraction (XRD), and (3) measuring the absorption spectrum by a spectrophotometer. The results of characterization experiments confirm that the grown fiber is indeed Yb:LiNbO₃ crystalline fiber. This unique crystalline fiber has multifunctional capability, including (1) a very effective low quantum defect lasing medium; (2) an electro-optically tunable medium, in which the refractive index of medium can be quickly tuned by the applied external electric field; and (3) a light guiding medium that offers the advantage of low driving voltage and power. The multifunctional capability of this crystalline fiber makes it very useful for a variety of applications such as highly compact, high-efficiency tunable lasers and filters.

For the waveguide displays, low diffraction efficiency and narrow response bandwidth at high spatial frequency limit the development of coupling elements. In this paper, a dual-monomer, with higher and lower refractive index modulation separately, allyl propionate H-PDLC system is proposed. After experimental optimization, the diffraction efficiency of prepared high transmittance (more than 90% in the visible spectrum) H-PDLC gratings is up to 91%, and the response bandwidth is 99 nm at 973 lp/mm. By increasing the proportion of initiator and changing the radiation conditions, the diffraction efficiency is optimized to 75.4% and the response bandwidth is 29 nm at 2941 lp/mm. The experiments demonstrate that the high-frequency H-PDLC gratings have considerable application prospects as coupling elements for augmented reality optical waveguide display systems.

We investigated the transmission properties of tapered fibres both experimentally with simulations in order to select the appropriate fibre for the high-resolution spectrograph EXOhSPEC. The work focuses on testing commercial produced graded-index (GI) and custom made graded-index (GI) multimode fibres and compares these with a 10 μm step-index (SI) conventional fibre. The performance of a spliced taper package (SP) is also investigated. All tests are performed with coherent light at 635 nm. The main focus of the investigation was to determine the factors that optimised the light transmission by matching the numerical aperture to the fibre and minimising misalignment. We characterised how the transmission through the fibre depends on the effective numerical aperture (NA_eff ) or input beam numerical aperture. The results suggest that under optimal coupling conditions, the transmission of a Custom GI taper is better than the 10 μm SI fibre and the commercial Thorlabs taper over the range of NA_eff from 0.02 to 0.25. In addition, we characterised a spliced taper package (SP) which contained a tapered fibre spliced to untapered fibre. Additionally a comparison of transmission via two coupling methods was investigated in the work. The results indicate splicing a large core GI fibre onto a tapered fibre is an appropriate technique for the fibre link of a fibre-fed spectrograph.

Optical fibers and waveguides designed for broadband infrared transmission, spanning approximately 1 micron to over 20 microns, have historically faced challenges such as high cost, brittleness, environmental susceptibility, and fragility, limiting their widespread practical use. In this paper, we introduce a new approach utilizing molten-core fiber manufacturing to create silver halide cores. The core composition shows improved broadband transmission, ranging from 0.6 micron to over 25 microns. Additionally, we report the fabrication of isotropic silver halide material with reduced crystalline scattering. The optical measurements and structural analysis of halide core material suggest the pathway for lower-loss infrared fibers and components with directly laser-written plasmonic structures.

Holographic elements fabricated based on photoalignment technology have advantages such as polarization sensitivity, high diffraction efficiency and small volume. Their applications range is becoming increasingly widespread. A liquid crystal (LC) holographic polarization variable line-space (H-PVLS) grating is fabricated in this paper. H-PVLS was analyzed from the perspective of microstructure and macroscopic properties. The microstructure at different positions of H-PVLS indicates the variable spacing properties of the fabricated holographic elements. Spectral analysis indicates that the variable spacing properties of H-PVLS results in a larger wavelength bandwidth compared to PVG under the same conditions. The anomalous dispersion properties of the fabricated components were also measured. These results of photoalignment-based H-PVLS grating provide valuable enlightenment to the development of near-eye displays and have the potential to improve the visual experiences.

In this paper, we introduce an approach—multiplexing gratings plus drive signal management scheme implemented on a micro-display device within an optical engine—to precisely adjust the color uniformity of an Augmented Reality (AR) eyewear display. This display is based on Volume Holographic Optical Elements (VHOEs) and a waveguide. Our method simplifies the complexity of multiplexing, requiring only a single optical waveguide and three RGB gratings for primary colors to achieve a full-color eyewear display with an expansive horizontal field of view (FOV) of nearly 30° and less than 3% ΔE_Lab color non-uniformity.

Volume gratings holographically written in a photorefractive material can be used for lensless image processing. This is because plane wave spectral components of an input image that are not at Bragg incidence are reflected with lower diffraction efficiency, so that higher spatial frequencies are transmitted. The dependence of edge enhancement on the spatial distribution of the grating, grating period, and angle of incidence of the incident optical field are investigated.

The performance of a combination the point cloud and layer-based method numerically to obtain a composite digital volume reflection hologram from digital transmission holograms is investigated. The 3D point cloud is reclassified into parallel two-dimensional layers. The digital transmission hologram is obtained from each layer. These layers can be at a specific wavelength or combination of wavelengths. This is followed by obtaining digital volume reflection holograms from digital transmission holograms using reflection grating theory, and then reading out the composite digital volume reflection hologram using coupled wave theory. Readout information from the digital volume reflection hologram with high wavelength selectivity is investigated.

We analyzed the strong impact of noise on the reconstructed images in a self-interference incoherent digital holographic (SIDH) system with spatially incoherent illumination. The analysis involved numerical modelling of the propagation and manipulation of the spherical waves emitted by the point sources that formed the object from the system entrance to the optical sensor, as well as recording of four 8-bit encoded phase-shifted incoherent holograms contaminated by detector shot noise. We synthesized a computer-generated hologram for the point sources in a plane parallel to the sensor plane, using our approach based on the similarities in the holograms of unit amplitude point sources. We assessed the quality of the reconstructed images using popular metrics such as MSE, PSNR, and SSIM. We compared simulation to experimental reconstructions and observed the same noise behavior in both cases.

LiTaO3 (lithium tantalate) crystal is widely used in infrared detection, acoustic surface wave devices and optical applications due to its outstanding piezoelectric, pyroelectric, and nonlinear optical properties. Over the past few decades, LiTaO3 single crystals have been studied intensively for their excellent acoustic and electro-optical properties. For the single crystal growth of LiTaO₃, raw materials of Li₂CO₃ and Ta₂O₅ need to be pretreated to form LiTaO₃ polycrystal. However, high temperature, more than 1200 °C and long heating time are required for adequate crystallization.

In this study, we prepared LiTaO₃ polycrystalline powder by solid state reaction synthesis from the raw powder of Li₂CO₃, Ta₂O₅, and cyanuric acid, which is an additive for a short reaction time and relatively low temperatures. The cyanuric acid, added into the mixture of Li₂CO₃ and Ta₂O₅, plays a role of fuel and inducer to produce intermediate compounds. Several temperatures and cyanuric acid composition ratio were employed to optimize the synthesis condition of pretreated LiTaO₃. Structural and composition analysis were conducted to characterize the synthesized LiTaO₃ powders. The optimized synthesis shows excellent ability to reduce lithium-ion volatilization and suggests an efficient way to manufacture high-quality LiTaO₃ polycrystalline powders.

Lithium tantalate (LiTaO3) crystal is widely used in infrared detection, acoustic surface wave devices and optical applications due to its outstanding piezoelectric, pyroelectric, and nonlinear optical properties. Over the past few decades, LiTaO3 single crystals have been studied intensively for their excellent acoustic and electro-optical properties. Today, most of LiTaO3 single crystals are made by czochralski methods, which is well-defined growing methods for high quality single crystal. To grow LiTaO3 single crystal in optimized condition, hot-zone structure should be designed properly. Temperature gradient, melt flow and heat dissipation should be optimized by managing the hot-zone structure. Especially, minimizing the heat dissipation and temperature gradient play a key role deciding the quality of grown single crystal.

In this study, we designed hot-zone structure in czochralski furnace for LiTaO3 single crystal growth. We added ring parts above the iridium crucible in which LiTaO3 crystal grow. It reduced heat dissipation and temperature gradient inside the hot-zone through bothering heat flow toward upper side of the system. Vertical and horizontal temperature gradient in whole range position was analyzed. Optimized size and position of ring parts were designed. For the simulation of this system, CGSim SW was used. We expect that our research results would contribute to the development of LiTaO3 single crystal growing technology.

An azobenzene holographic material based on the {[4-(dimethylamino) phenyl] diazenyl} benzoic acid (Methyl red) for dynamic holographic recording is synthesized. The first order diffraction can be detected in 0.5 seconds. The rapid response in holographic recording /erasing makes it possible in dynamic applications.

A phase unwrapping method based on the phase-wedged encoding algorithm for phase-shifting projected fringe profilometry is presented. The patterns used to perform the phase-shifting technique can be used for unwrapping directly. Even though the size of the inspected objected is so small that only one fringe is projected, fringes can be discerned correctly.

A facile fabrication route using hierarchical mesoporous silica materials for anti-reflection films is presented. The graded index design makes the refraction index changes slightly between any two laminated layers, resulting in a minimized reflectance coefficient.

A signal processing algorithm is presented for 3D profile measurements by means of coaxial fringe projections. It helps to reduce the noise caused by low reflectance and enhance the systematic reliability. Accuracy of the retrieved 3D profile can be achieved in the order of sub-millimeters.

In this paper, we will discuss about the color performance and image quality of the Volume-Holographic-Optical-Element (VHOE)-based AR devices using two different type of volume holograms: transmission or reflection-type VHOEs. The simulation results show that color distortion occurring in these two types of VHOE-based AR devices are quite different and resulting from different characteristics of Bragg diffraction from those VHOEs. The reflective VHOE-based AR devices show better overall performance in terms of color, field of view and image quality.

A one-shot projection scheme using the phase-shifting technique to describe the profile of the dynamic object is presented. A color-encoded pattern is employed to perform the one-shot measurement. With the proposed scheme of calibration, errors caused by cross-talk between the color channels can be reduced.