Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications XVIII

Keywords: silicon UV sensors, high entropy alloys, multi-beam puls Sensitivity improvement of ultraviolet (UV) photodetectors can be achieved by integrating them with down-converting photoluminescent (PL) nanocomposites enriched with the nanoparticles of multi-metal alloys. We report on the multi-metal alloy PL nanocomposites made using the recently invented method of the concurrent multi-beam multi-target pulsed laser deposition (CMBMT PLD). We used ultraviolet (UV) durable polymers CORIN XLS and Optinox SR as matrices for the nancomposites. The surface plasmon polariton (SPP) tuning range of the bimetallic Au-Ag nanocomposite was, for instance, between 400

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Our focus on silicon photonics addresses the challenge of NIR photodetection. We introduce a novel method embedding graphene (Gr) between crystalline (c-Si) and hydrogenated amorphous silicon (a-Si:H) to overcome it. This method enhances light-matter interaction, precisely confining the optical field where Gr is placed. We integrate the photodetector (PD) into a Silicon-On-Insulator waveguide, revealing a new photoconversion mechanism induced by traps at the Gr/a-Si:H interface. These traps release charge carriers into graphene under NIR light, boosting the generated current. In our PD within the a-Si:H/c-Si waveguide, Gr is positioned where field intensity peaks, maximizing interaction at 1.55 μm. Numerical simulations fine-tuned waveguide dimensions for optimized performance. Preliminary optical characterization shows promising responsivity evaluation of 0.22 A/W at 1550 nm wavelength under a reverse bias of –10 V applied to the PD. These findings signify a significant advancement in silicon photonics research.

We study optical limiting by a system of coupled optical cavities with a PT-symmetric spectrum of reflectionless modes. The optical limiting is associated with violating the PT symmetry due to the thermo-optic effect in one of the cavities. In our experimental implementation, we use a three-mirror resonator with PT-symmetric spectral degeneracy of reflectionless modes made of alternating layers of cryolite and ZnS. Compared to existing limiter designs, the introduced optical limiter offers a custom limiting threshold, high damage threshold, nanosecond activation time, and broadband laser protection. Optical limiting is demonstrated by single 532-nm 6-ns laser pulse measurements and thermo-optical simulations.

Zinc Oxide (ZnO) is a long-studied material that possesses properties well-regarded for their applications in photonics, optoelectronics, and nanoscience. While much research exists detailing conventional deposition (i.e. vapor phase, sol gel) and post processing (thermal) techniques, the effects of photonic annealing techniques such as intense pulsed light annealing (IPLA) on thin film of ZnO remain less explored. This research effort examines the outcomes of applying IPLA to ZnO in various scenarios, including inkjet printed and spin coated films, and with inks prepared from nanoparticle suspensions and metal-organic salt solutions. The findings indicate that IPLA can create film morphologies distinct from those achievable with conventional thermal annealing methods. The study employs a range of material assessment techniques including the electronic characterization of films, scanning and transmission electron microscopy, and analysis using FT-IR and UV-Vis spectroscopy, to elucidate the impact of IPLA on ZnO films under diverse conditions.

Multiferroic magnetoelectric composite materials are studied due to their potential applications in sensors, actuators, and other electronic devices. Inkjet printing is a direct write additive manufacturing method capable of fabricating structures on the micrometer scale by depositing solutions containing functional nanomaterials. In this study, finite element simulations were used to investigate the response of these materials under different magnetic and electric fields, revealing that the magnetoelectric coupling coefficient of the composites is highly dependent on the orientation of the magnetic and electric fields with respect to the composite material. The simulations also showed that the composites exhibit a strong nonlinear behavior, which is attributed to the magnetostrictive properties in the cobalt ferrite phase. Experimental results are compared to validate numerical simulations. Further simulation experiments were undertaken considering the capabilities of inkjet printing additive manufacturing to inform the fabrication of electronic devices.

The integration of Electronic IC (EIC) and Photonic IC (PIC) on silicon-on-insulator platforms drives the advancement of silicon photonics (SiPH). However, concerns arise regarding supply chain vulnerabilities, particularly in the face of traditional imaging techniques such as surface acoustic wave (SAW) and e-beam probing. These methods, employed in failure analysis, pose risks to data integrity within silicon photonics chips, making them susceptible to physical intrusions aimed at reliability testing. Our research aims to comprehensively understand the impact of ultrasound-induced vibrations and e-beam interactions on critical parameters of photonic chip components. Through experimental quantification, we assess vulnerabilities, including data degradation and transmission alterations. Proposed countermeasures include the implementation of passivation layers and advanced materials to mitigate risks and enhance reliability. This study offers insights into safeguarding silicon photonics against physical intrusions, ensuring robustness in communication applications.

A volume holographic material based on the ethylene glycol phenyl ethyl arylate (EGPEA) monomers with various initiator concentrations in the host matrix PMMA is synthesized. For a polymer with a thickness of 190m and an illuminating power density of 2mW/cm2, a Bragg grating with the diffraction efficiency of 95% can be formed in 80 seconds.

In this paper, we discuss the fabrication of micron/nano structures in functional crystalline materials by femtosecond laser inscription. Functional crystals, including electro-optic (EO) crystals such as lithium bate, KTN and lasing medium such as Ti:sapphire are explored. Different writing methods such as direct writing, interference writing are discussed.

In this paper, we investigated the rare earth doped electro-optic crystals. Rare earth elements such as Er, Yb are included. The electro-optic crystals such as lithium niobate and KTN are discussed. In addition to the bulk form crystal, the crystalline fiber form is also addressed.

Cadmium silicon phosphide, CdSiP2 (CSP), crystals have good nonlinear optical properties resulting in their use in optical parametric generation (OPO and OPA) of mid-infrared light. One common limitation on the performance of OPO materials is residual optical absorption which often results from point defects formed during crystal growth. Electron paramagnetic resonance (EPR) is a powerful technique for identifying and tracking point defects in materials. By correlating behaviors of native point defects exposed to 1064 nm light using EPR with changes in optical absorption bands, models are proposed for three of the observed broad optical absorption bands.

The coded-aperture imaging technique needs only a thin coded mask to encode image, which enable to build an ultra-thin imaging system. However, the limited dynamic range of the image sensor and the diffraction effect degrades the reconstructed images quality. Here, we proposed an integrated ultra-thin coded aperture lensless camera. We take Fresnel zone plates as coded mask, then the incident light could be encoded into a hologram-like pattern, and the image can be holographic reconstruction. A deep neural network is also trained for rapid and high-quality reconstruction. To improve the dynamic range, differential-enhancement method is used by capture two complementary encoding images. The proposed integrated ultra-thin camera is expected to be applied in unconscious payment, identification and authentication, autonomous cars, etc.

Holographic Polymer dispersed liquid crystal（H-PDLC）grating element has hope to solve the above problems because of the higher reflective index modulation, electronically controlled and great optical properties. In this paper, a dual-monomer allyl propionate H-PDLC system is proposed by changing the component of prepolymers to improve the holographic properties of the grating, which consisted of TMPTA/EP828. The spatial frequency of the grating is increased based on this system to meet the requirements of waveguide displays. we optimized by increasing the proportion of initiator and changing the exposure conditions. It indicated that the transmittance of H-PDLC is greater than 90% in the visible band, the diffraction efficiency is greater than 91%, and the response bandwidth is up to 99nm at 973lp/mm. At 2941lp/mm, the diffraction efficiency is over 75.4% and the response bandwidth is up to 29nm. Therefore, high-frequency H-PDLC gratings have considerable application prospects as coupling devices for augmented reality optical waveguide display systems.

The work presented explores the integration of in-line Fabry-Perot interferometric (FPI) microcavities along tapered gold nanoparticle-coated optical fiber biosensors to enhance surface plasmon resonance (SPR) based sensing. The study focuses on optimizing plasmonic performance, evaluating response to refractive index changes, and incorporating microcavities as localized resonators. The biosensor demonstrated promising results in detecting glucose concentrations, with a potential for multiparameter biosensing and signal demultiplexing, contributing to the advancement of Lab-on-Fiber biosensor technology.

We investigated the impact of taper length on light transmission through tapered graded-index fibres. We tested commercial fibres from Thorlabs and a custom graded-index fibre using both coherent and incoherent light sources. We also measured the modal noise power fluctuations caused by bending the fibre.

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, hampering their widespread practical use. In this paper, we introduce a breakthrough approach utilizing molten-core fiber manufacturing techniques to create cores infused with silver halide. Our core composition showcases remarkable broadband transmission capabilities, ranging from 0.5 micron to over 25 microns. Additionally, we detail the fabrication of isotropic silver halide material with minimized crystalline scattering. The optical measurements and structural analysis conducted on the core materials provide promising insights, paving the way for the production of low-loss infrared fibers on a larger scale.

Planar photonic devices prepared based on liquid crystal photoalignment technology have advantages such as polarization sensitivity, high diffraction efficiency, and small volume, and their application range is becoming increasingly widespread. Based on the interference of orthogonal cylindrical and plane wave, we prepare a liquid crystal (LC) polarization variable line-space (VLS) grating. The VLS characteristics of the gratings were analyzed from a polarization perspective for the first time, and the grating period of the VLS grating at different positions was calculated. The relationship between the variable line-space characteristics and the angle between two orthogonal polarized beams was studied. We prepared liquid crystal polarization planar VLS gratings and VLS volume gratings, and studied their diffraction efficiency, variable spacing, and other characteristics. The relationship between spectral changes of VLS gratings and UV curing time was also studied. LC polarization VLS gratings have important applications in pupil extension for head mounted displays such as AR/VR and smart windows.

In this presentation, we will delve into the evolution of volume holographic optical elements (VHOEs), discussing their development alongside calculation models such as the VOHIL model. We will unveil a novel visualization scheme rooted in this model, aimed at elucidating Bragg diffraction within intricate volume holograms. Lastly, we will showcase the latest advancements in the application of VHOEs, particularly in the realm of lightguide-based Augmented Reality (AR) and Mixed Reality (MR) glasses.

The CGH technique is crucial for MR displays, resolving the VAC issue with three-dimensional image generation. However, drawbacks include excessive device volume and speckle noise from coherent light. The lightguides with VHOE couplers and LED light source are employed to address these issues. In this study, we employed an LED as the light source to reduce the speckle noise. The volume holographic optical elements (VHOEs) as the in-coupler and out-coupler are designed as bandpass filters. The VHOEs filtered the CGH display's effective wavelength to inhibit image degradation caused by dispersion. Furthermore, the aberration caused by the lightguide was analyzed and compensated in this study. The design method, simulation results, and experimental results are discussed in this work.

Conventional calculation of performance based on M/# assumes the diffraction efficiency as a simple function of the material thickness. It ignores the three-dimensional distribution of refractive index, which contributes to different diffraction efficiency, and always leads to over-evaluation of the storage capacity. Therefore, we proposed an efficiency coefficient to calculate the diffraction efficiency per refractive index consumption.

Augmented Reality (AR) and Mixed Reality (MR) glasses stand as pivotal technological advancements in contemporary society. However, maintaining a compact and lightweight design while ensuring high-quality image viewing remains a persistent challenge. Researchers endeavor to overcome the intricate optical hurdles associated with these glasses. They suggest that waveguides incorporating two in- and out-coupling Volume Holographic Optical Elements (VHOEs) has surfaced as a promising approach, addressing these requirements and providing high see-through transmittance due to Bragg selectivity. Nonetheless, in the case of a full-color VHOE-based waveguide, the crosstalk between the RGB gratings of three primary colors within a waveguide results in the ghost images that diminish image quality. In this paper, we propose a method to eliminate ghost images and offer precise simulations aligned with experimental observations.

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% ΔELab 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, angle of incidence of the incident optical field are investigated.

The performance of the combination the point cloud and layer-based methods to numerically obtain digital volume reflection holograms from digital transmission holograms is investigated. The 3D model points are classified into parallel two-dimensional layers. The digital transmission hologram is obtained from each layer. These layers can be at specific wavelength or combination of colors. This is followed by obtaining digital volume reflection hologram from digital transmission hologram using reflection grating theory, and then reading out the digital volume reflection holograms using coupled wave theory. Readout of the digital volume reflection hologram, which results in high wavelength selectivity, is investigated

Near-eye-display has shown the potential to be the next-generation consumer interface to the digital devices. Among many techniques, exit-pupil-expansion (EPE) technique promises a simple and compact architecture. The volume-holographic-optical-element (VHOE) based EPE shows a lot of advantages based on multiplexing capability. However, only specific wavelength in each corresponding angle can passed through the VHOE based EPE technique. In this paper, we build-up an optical model to predict the wavelength distribution of the VHOE-based EPE.

We analyzed two noise sources in order to explain strong noise impact usually observed for the reconstructed images in a SIDH system with spatially incoherent illumination. The analysis involved numerical modelling of the propagation and manipulation of the spherical waves from the point sources that formed the object to the optical sensor, and recording of four 8-bit encoded phase-shifted incoherent holograms with 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 studied the noise impact depending on such parameters as the number of the point sources in the object and the irradiance within the exposure interval. We also compared the results of simulation to the experimental reconstructions.

This talk will consider the future of metal halide perovskite (MHP) photovoltaic (PV) technologies as photovoltaic deployment reaches the terawatt scale. The requirements for significantly increasing PV deployment beyond current rates and what the implications are for technologies attempting to meet this challenge will be addressed. In particular how issues of CO2 impacts and sustainability inform near and longer-term research development and deployment goals for MHP enabled PV will be discussed. To facilitate this, an overview of current state of the art results for MHP based single junction, and multi-junctions in all-perovskite or hybrid configurations with other PV technologies will be presented. This will also include examination of performance of MHP-PVs along both efficiency and reliability axes for not only cells but also modules placed in context of the success of technologies that are currently widely deployed.

The recent advent of robust, refractory (having a high melting point and chemical stability at temperatures above 2000°C) photonic materials such as plasmonic ceramics, specifically, transition metal nitrides (TMNs), MXenes and transparent conducting oxides (TCOs) is currently driving the development of durable, compact, chip-compatible devices for sustainable energy, harsh-environment sensing, defense and intelligence, information technology, aerospace, chemical and oil & gas industries. These materials offer high-temperature and chemical stability, great tailorability of their optical properties, strong plasmonic behavior, optical nonlinearities, and high photothermal conversion efficiencies. This lecture will discuss advanced machine-learning-assisted photonic designs, materials optimization, and fabrication approaches for the development of efficient thermophotovoltaic (TPV) systems, lightsail spacecrafts, and high-T sensors utilizing TMN metasurfaces. We also explore the potential of TMNs (titanium nitride, zirconium nitride) and TCOs for switchable photonics, high-harmonic-based XUV generation, refractory metasurfaces for energy conversion, high-power applications, photodynamic therapy and photochemistry/photocatalysis. The development of environmentally-friendly, large-scale fabrication techniques will be discussed, and the emphasis will be put on novel machine-learning-driven design frameworks that leverage the emerging quantum solvers for meta-device optimization and bridge the areas of materials engineering, photonic design, and quantum technologies.

In the present research work, tungstate phosphors doped with Dysprosium (Dy3+), Samarium (Sm3+) and Europium (Eu3+) ions were synthesized using traditional high temperature reaction method. The white, orange-red, and red region applications of the synthesised phosphor material are approved by the structural and photoluminescence (PL) studies. Diffuse reflectance spectra (DRS) have been used to calculate the optical band gap value. The photoluminescence (PL) spectral features recorded for the Dy3+, Sm3+ and Eu3+ ions activated tungstate phosphors under 368, 336 and 394 nm excitation reveal strong emission peaks in different regions and therefore, evaluated CIE chromaticity coordinates found to be in white (0.32767, 0.36616), orange-red (0.57925, 0.41899) and red (0.62683, 0.37272) regions. The calculated CCT values for Dy3+ and Sm3+ & Eu3+ ions signify their application for cool and warm white light-emitting diodes (w-LEDs), respectively. All the above investigations help us to study the PL properties of different dopant ions in a host and signify their suitability for cool and warm w-LEDs.

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In this paper, we have demonstrated a high-average-power and high-energy nanosecond all-fiber MOPA system with a pulse-shaped diode seed laser and an extra-large-mode-area (XLMA) Yb-doped dual cladding fiber as gain fiber in the power amplifier. At the repetition rate of 50 kHz, a maximum average power output of 1021 W was obtained, corresponding to a single pulse energy of 19.5 mJ and a peak power of 384.5 kW. At the repetition rate of 250 kHz, the maximum average power of 1529 W with a high slope efficiency of 82.1% was achieved. Such high-efficiency, high-energy, high-average-power MOPA systems have a wide range of applications, including material processing, marking and laser cleaning owing to their compact structure, stability and reliability.

In this work, we present an efficient detection of hydrocarbons, i.e. ethane (C2H6), and characterized by very broad absorption spectra pentane (C5H12) and butane (C4H10) within 2900 cm-1 to 3100 cm-1 wavelength band using a 26.15 m long, all-silica, self-fabricated antiresonant hollow-core fiber (ARHCF). The developed broadband gas sensor relies on the unique combination of the gas-filled ARHCF forming a low-volume, long and compact absorption cell and optical frequency comb Fourier transform spectroscopy technique. The sensor is characterized by a superb capability of retrieving broad molecular transitions with a detection capability greater than multipass cell-assisted and comb-based photoacoustic spectrometers.

The generation of nonlinear phenomena on integrated platforms other than silicon-on-insulator (SOI) is becoming increasingly imperative. This necessitates a meticulous study of potential alternative platforms and wavelengths within the mid-infrared and near-infrared ranges. The use of the SOI platform is limited due to silica absorption at wavelengths above 3,6 μm. Therefore, it is necessary to search for materials that exhibit an appropriate transparency window for these wavelengths. In this work, we have used the D-Scan technique to design, characterize, and analyze materials in fibers and integrated photonic circuits. We present studies of these materials in the range of 0.7 μm to 4 μm. The goal is to provide figures of merit to assist in the selection of the most suitable material platform for specific nonlinear phenomena at specific wavelengths, enabling subsequent applications across different areas.

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 0.3 seconds. Without holographic recording, the grating disappeared 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 method to fabricate graded-index layers by means of mesoporous materials is presented. Reflectance coefficients with large incident angles for various wavelengths is simulated as well.

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 of the HOE-based AR device using either transmission or reflection type HOEs for image coupling-in and -out. We first build up a theoretic optical model to calculate the color coordinate of each pixel of projected virtual image while a white image is transmitted. During the calculation, the color gamut of each pixel of projected virtual image can be obtained. The simulation results show that color breaking occurs due to the Bragg selectivity of each grating and image shifting caused by the extended eye-box. Moreover, the thickness of the waveguide also causes uneven color distribution. These calculations provide a way to compare the color performance characteristics between waveguides using transmission and reflection type HOEs, clarifying the color performance of HOE light guides, rendering them suitable for high-quality AR near-eye glasses.

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.

Indium tin oxide (ITO) thin films are widely used many optoelectronics instruments like flat panel display, organic light emitting diodes, transparent transistors etc. as a transparent and conducting electrodes due to the high visible transparency and electrical conductivity. The properties of ITO films can be controlled by controlling the various deposition parameters of the sputtering system like gas flow rate, applied power, substrate temperature, deposition pressure etc. Rapid thermal annealing (RTA) is also an emerging post-deposition technique utilized for enhancement of the various properties of the deposited films. In the normal RTA process, the temperature of the chamber was increased with the rate of about 20°C/s and then decreased with the nearly same rate. RTA process helps in enhancement of optical and electrical properties of TCO films. In this research, the ITO films were deposited on glass substate in argon atmosphere without oxygen at room temperature. Then RTA was applied to the deposited films. The effect of RTA for 1 to 10 minutes on optical, electrical, and structural properties of the ITO films was studied in this research.