This PDF file contains the front matter associated with SPIE Proceedings Volume 12416, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Hexagonal III-nitride semiconductors exhibit internal polarization fields along their c-direction. In regions with graded mole fractions, the polarization gradient creates bound volume charge densities. Due to their electrostatic effect, they affect the balance of mobile charges, and can lead to polarization induced doping. In this contribution, drift-diffusion type simulations are employed in order to analyze a pn-junction based on polarization induced charges, and an analytical formula for calculating the bound charge density is given.

In an optical wireless communication system, the LEDs require high bandwidth to achieve data rates compare to RF communications. Therefore, it is preferred to use high current densities to drive the LED, even beyond its maximum efficiency point. Nevertheless, the LED is a self-heating device where part of the electrical power is converted to optical power and the rest into heat. This increment of temperature in the LED will reduce its optical power and efficiency, causing a degradation of the optical system SNR. Firstly, we start by deriving the relationship between the LED voltage with its junction temperature using the Shockley equation. Then, we measure the forward voltage at different temperatures to prove a linear relation between them. The optical power, LED bandwidth, and efficiency can be calculated using the ABC parameters from the rate equation. Therefore, we propose a method to obtain these parameters by measuring the emitted optical power and its rise time when varying the driving current. Finally, the ABC parameters are calculated by solving an MMSE problem with the measurements previously done. The throughput of an optical wireless link depends on the efficiency and the LED bandwidth, thus it is temperature dependent. We calculate the degradation of the rate caused by the temperature increment.

Semiconductors are amongst the most efficient active laser media as they yield extreme wall-plug efficiencies. Their broad gain bandwidth also promise short-pulse operation. Yet, intrinsic charge-carrier relaxation dynamics limit the feasible repetition rates beyond constraints of cavity design and heat removal. In lieu of studying an operation device we monitor the population dynamics, i.e., the initial buildup of gain after optical excitation as well as its recovery after a stimulated emission process using multiple pump-probe spectroscopy. The first optical pulse injects hot charge carriers that eventually build up spectral gain in the sample. The energies are chosen such to mimic typical electrical injection surplus energies. Subsequently, a second laser pulse tuned to the broad spectral region in which gain is observed is used to stimulate emission and thus eliminate the gain. Analysis of the absorption spectra after stimulated emission reveals gain recovery times in the picosecond regime.

In this work, we explore the band edge absorption characteristics of semiconductors as applied to optoelectronic modulation—with careful consideration to the departures from ideality in the semiconductors. To this end, we develop a rigorous model of electroabsorption in semiconductors that characterizes the electric-field-induced constriction/narrowing of the bandgap and the resulting increase in absorption of photons, whose energies are slightly below the bandgap energy. The model unifies the Franz-Keldysh effect, characterizing the electric-field-induced tunneling of photoexcited electrons from valence band states to conduction band states, and the Einstein model, quantifying the encroachment of valence and conduction band states into the bandgap. Careful consideration is given here to the nonidealities in the semiconductor, which arise within the valence band as degenerate states, due to light and heavy holes, and within the bandgap, as encroaching Urbach tail states. We apply the model in characterizing optoelectronic modulation of 980-nm photons with semi-insulating indium phosphide (SI-InP), and we see strong agreement between our theoretical and experimental results over a wide range of electric fields and photon energies. Ultimately, the findings show that optoelectronic modulation can be had with large modulation depths over short propagation lengths through the semiconductor. This opens the door to highly effective implementations of optoelectronic modulators in emerging free-space optical communication systems—given that such modulators do not allow for prolonged (guided-wave) propagation and have thus exhibited small modulation depths.

Extending the wavelength response of short-wavelength infrared detectors (SWIR) to 2 μm and beyond offers a key enabling technology for Lidar, spectroscopy, and imaging applications. Lattice-matched InGaAs/GaAsSb type-II superlattices (T2SL) have demonstrated SWIR detection around 2 μm on a highly producible InP platform but are limited in further extending wavelength response out to 2.5 μm. Introducing strain between alternating periodic layers of the superlattice provide a means to further extend wavelength while maintaining a strain balance (net zero strain). Numerical modeling utilizing 8 band k.p simulations were studied to examine the impact of bandgap energy, quantum confinement, and strain on the effective bandgap, wavefunction overlap, and corresponding absorption strength. T2SL with 4.73 nm In_0.52Ga_0.48As and 4.5 nm GaAs_0.48Sb_0.52 demonstrate extended wavelength response with absorption coefficient ~1000 cm-1 around the cutoff wavelength and over most of the 2-2.5 μm range indicating efficient overlap between the wavefunctions and high quantum efficiency values. Effect of period thickness, and strain on absorption coefficient and effective bandgap is analyzed and compared with the lattice matched case. Devices were fabricated with the superlattice structure as the absorber layer (3 μm thick) in a p-i-n photodiode configuration. Dark current voltage characteristics were measured and compared with simulated results. Measured dark current values were comparable to those of lattice-matched InGaAs/GaAsSb type II superlattices without extensive device optimization. Simulated quantum efficiency results showed clear extended cutoff of 2.5 μm with high quantum efficiency values in the 1.4-2.1 μm spectral region and features that closely follow absorption spectra validating the suitability of the strainbalanced approach in reducing the effective bandgap values while maintain absorption strength.

Microcrystalline Silicon-Germanium (μc-SiGe:H) is a low bandgap material whose optical and electrical properties strongly depend on deposition conditions. In this work, an above integrated circuit (above-IC) [1]–[3] compatible, near infrared (NIR) sensor based on microcrystalline Silicon-Germanium is produced and characterized. The N-I-P photodiode is obtained by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) from a SiH₄ + GeH₄ + H₂ gas mixture. Quantum efficiency measurements reveals a 60 at.% Ge fraction is optimal for a 200 nm thick μc-SiGe:H intrinsic absorber layer. Above this threshold, the degradation in electrical properties prevails on the gain in absorption.

We study the impact of hole traps on the optical response of Si waveguide-coupled p-i-n In_0.53Ga_0.47As photodetectors. Compared with the ideal case, a trap density of 1e14 cm^-2eV^-1 at the In0.53Ga0.47As/SiO₂ interface reduces the device’s quantum efficiency by about 10% and its cut-off frequency by a factor of 2. The drop of the quantum efficiency is mainly caused by interface traps at heavily doped regions, whereas the cut-off frequency degrades due to interface traps at the i-region. Hole traps at the In_0.53Ga_0.47As/Si interface, however, have no effect on the quantum efficiency - only the cut-off frequency drops with increasing trap concentration. Similar impacts of such traps are observed in plasmonic waveguide-coupled photodetectors with a metal strip placed on top of the i-region.

High sensitivity near-ultraviolet (NUV) avalanche photodiodes operating at wavelengths longer than 300 nm are useful for various applications, including surface exploration of Ocean Worlds and other planetary bodies via Raman spectroscopy. 4H-SiC has long been established as a proven UV detector technology; however, the responsivity of 4H–SiC avalanche photodiodes (APDs) diminishes dramatically at wavelengths longer than ≈ 280 nm due to its weak absorption at wavelengths approaching the indirect bandgap. The authors will present on the design and optimization of 4H-SiC separate absorption, charge and multiplication (SACM) APDs for broadband absorption from 266 to 340 nm.

Single-photon avalanche diodes (SPADs) are high-performance light-sensitive sensors operating in low-light condition. Si-SPADs manufactured through standard CMOS fabrication process have advantages in terms of manufacturing cost, low power consumption, device shrinkage, and process stability compared to SPADs on custom fabrication. A deeper multiplication using deep n-well (DNW) improves key performances of Si-SPAD such as dark count rate (DCR) and photon detection efficiency (PDE). Here, the guard ring (GR) must be included for deep junction SPAD because light detection efficiency is lowered due to premature edge breakdown (PEB) generated by strong electric field at the edge. PEB affects not only the characteristics but also the manufacturing uniformity. Therefore, the DNW should be carefully designed to show better performance and stability for Si-SPADs. In this paper, the effects of electrical characteristics such as current-voltage (I-V) curve, DCR, off leakage, and breakdown voltage, and process stability on DNW implanted SPAD with GR variation are analyzed using actual fabricated SPAD measurement data and the calibrated technology computer-aided design (TCAD) simulated results. When the deep multiplication junction is formed using the higher ion implantation energy, the penetration effect and the process instability can be generated and it can also weaken the GR effect, which prevents PEB caused by having a stronger electric field than the multiplication zone. In addition, it is verified to prevent the risk of designing a Si-SPAD and die-to-die variation due to DNW implantation. Based on the results, deep junction design scheme for high resolution and mass production can be suggested.

Superconducting nanostripe single-photon detectors (SNSPDs) represent key components in silicon quantum photonic integrated circuits (SiQuPICs). They provide good timing precision, low dark counts, and high efficiency. The design, fabrication, and characterization of SiQuPICs comprising SNSPDs coupled to dielectric optical waveguides are the core objectives of our work. The detectors are positioned directly on the dielectric waveguide core to increase photon absorption by the superconducting nanostripes. We also present results on the SPICE circuit modeling of traveling-wave SNSPDs integrated with Si₃N₄/SiO₂ optical waveguides.

Curved imaging sensors bring significant size, weight and cost reduction to imaging systems while mitigating offaxis optical aberrations, as opposed to current flat sensors. Unlocking these key features has captured the interest of major players over the last two decades. SILINA has been developing a CMOS Image Sensor (CIS) curving process, which adapts to various sensor characteristics. This enables to maximize the optical performance of every single imaging system. We have demonstrated the manufacturing of curved CMOS Front-Side Illuminated (FSI) and Back Side Illuminated (BSI), opening a new area of compact, fast, wide-angle and high-resolution optical lenses. An EMVA1288 compliant CMOS image sensor characterization testbeds has been developed in order to measure the electro-optical performances of curved CIS. Experimental data of dark current, photo-response nonuniformity, fixed pattern noise, quantum efficiency and more can be measured. In parallel to the electro-optical characterization campaign, reliability tests such as thermal tests (ageing, cycling) have been performed. This paper gives an overview of SILINA‘s main technological developments and electro-optical performance of CMOS Back Side Illuminated (BSI) curved image sensors is presented.

Distributed feedback lasers are key ingredients of high-speed, high-capacity integrated photonic chips. In this work, we extract the linewidth enhancement factor above threshold by measuring the transitional points in the optical-injection stability map from a quantum well distributed feedback laser with a temperature-controlled mismatch between the lasing and optical gain peaks. This unique measurement technique allows the simultaneous extraction of important parameters influencing the linewidth, particularly the photon lifetime. When the current is higher than twice threshold and 50 ℃, the linewidth enhancement factor is smaller than that at 10 ℃. This effect is attributed to the increasing differential gain at the lasing peak position, which is a result of the larger optical mismatch. We also measured the spectral linewidth at different temperatures, which then yields the spontaneous emission factor, n_sp. Due to the low linewidth enhancement factor at high temperatures, a large photon lifetime, and a modest increase in n_sp, the linewidth does not drastically increase with pump current and stays below 100 kHz at 50 ℃. Overall, the stability of the linewidth enhancement factor combined with the large optical mismatch brings a relative temperature insensitivity, which is of paramount importance for applications requiring high-temperature operation and improved coherent light.

The concept of the Isochrons is introduced for the study of the phase response of an optically injected semiconductor laser. The global structure of the Isochrons and the corresponding phase response curves are numerically computed and systematically dissected in terms of their characteristics. Their paramount role in the synchronization properties under an external periodic modulation of the injection beam is shown along with their ability for providing conditions for stable phase locking and highly customizable periodic outputs with discrete equidistant spectra in the form of frequency combs. Potential applications related to remote clock synchronization for communications requiring coherent receivers as well as geolocation applications based on precise phase-shift measurements, are discussed.

In this work we provide a numerical simulation for doped silicon nanosphere with a validation using 3D FDTD commercial kit (Lumerical). We have calculated the absorption efficiency of silicon microspheres of different doping concentration based on Mie resonance. Meanwhile, filling the surrounding medium with specific gases which have absorption in the MIR region changes the calculated spectrum. The input parameters for this simulation were the radius of the sphere, the complex refractive index of the sphere’s material and the host gas, and the targeted wavelength range. The absorption spectra were calculated for a silicon microsphere of radius 0.5 microns and different doping concentrations. In each case, the microsphere is surrounded with air and then with Methane. There is no peak shift between the two curves. However, there is an oscillation in the curve of Methane in the wavelength range where the absorption region of Methane lies. Increasing the doping concentration of silicon makes the absorption curve of sphereair shift to the left (blue shifted). This in turn makes this oscillation more visible, especially at doping concentration of 5×10²⁰ cm^-3. This can be explained that, increasing the doping concentration makes the silicon sphere more metal alike and increases in turn the surface plasmonic effect. That opens the door for multitude of sensing applications using the concept of Mie resonance.

Reduction of mobile mechanical parts in Optical Phased Arrays and the overall miniaturization of the system can be claimed to improve robustness to harsh environment condition and reduction of the overall power consumption. An optical phased array configuration built on structure developed in a silicon photonic integrated circuit technology, may be able provide a solution to fit these requirements. Nevertheless, there is some drawback and some fabrication complexity that can be limiting the direct application for automotive solution in a low-cost configuration. In this work, it is presented the design and the simulation of an amorphous silicon phased array working at a wavelength of 1550 nm. Potential and limitation of this approach will be outlined.

A novel optical gas sensor based on electromagnetically induced transparency (EMT)is proposed. In this paper we propose plasmonic non concentric ring resonators resonate near the absorption regions of many gases in the mid-infrared region. Mid-infrared (MIR) wavelength range is of particular interest because it contains the absorption resonance for several molecules such as methane, carbon dioxide, carbon monoxide, and acetone. The sensing process is controlled by changing the refractive index. The proposed slotted waveguide coupled with double non-concentric ring resonators, both the waveguide and rings are surrounded with doped silicon. Doped silicon can act as a suitable plasmonic alternative instead of metals in the MIR range. When the two coupled non-concentric rings optimize to resonate on the same wavelength; interesting phenomena occurs such as the Fano-resonance and the electromagnetic induced transparency effects. In this paper we show the electromagnetic induced Transparency which is an absence of the resonant spectral lines of the same wavelength, and the creation of two resonance lines at red-shifted and blue-shifted wavelengths. Moreover, we mentioned all the details about the dimensions and the material used for our design. A Small foot print, high sensitivity, and high Figure of merit are achieved.

Graphene has demonstrated significant advantages in the field of sensing due to its unique electrical and optical properties in the THz regime. Graphene sheets can support surface plasmon polaritons (SPPs) under specific conditions. In the present analytical and numerical study, we analyzed the tunability of the plasmonic sensor based on the surface conductivity of graphene. The analysis has been done with TM polarized waves. The performance parameters of the plasmonic sensor, such as sensitivity, are also tuned and calculated in the present study.

Rigorous Coupled Wave Analysis (RCWA) method is highly efficient for the simulation of diffraction efficiency and field distribution patterns in periodic structures and textured optoelectronic devices such as VCSELs, LEDs, and DOEs. RCWA provides exact solutions provided the Fourier expansion has infinite order. In practice, the Fourier expansion must be truncated due to computer memory limitations. Researchers are trying to utilize fast convergence algorithms such as the ‘normal vector method’ and ‘Li’s rule’ which could obtain accurate TM mode results with fewer Fourier orders. However, to thoroughly investigating the behavior of a structure usually requires thousand and even millions of RCWA simulations which may last hours and days. GPU is highly suitable for solutions of complex systems allowing large-scale multi-threaded parallel programming (< 1000 / low-end GPU, <5k / high-end GPU) to speed up matrix computations significantly. In this paper, we present a high-speed RCWA program utilizing optimized CUDA-GPU code and MAGMA libraries. It achieves 2-6 X speedup compared to conventional multithreaded CPU-based code utilizing the Intel MKL library running on IRIDIS 5 super-computer (1 NVIDIA v100 GPU, 40 Intel Xeon Gold 6138 2.0GHz cores CPU)

Accurate simulation is a critical requirement for modern optical systems, but precise theoretical modeling can be challenging due to various factors such as misalignment, theoretical approximations, and instrument errors. This paper presents the black-box simulation method, which addresses these limitations by training the optical system model using the optical field outputs. This approach leads to more accurate simulations, making it possible to effectively train optical Neural Network systems for improved performance.

This paper aims to improve the post-fabrication transmission performance of nested hollow-core fibers (HCF) by incorporating random perturbations inside the cladding structure in the fiber model and evaluating their impact on the overall guidance performance by applying a Monte-Carlo simulation strategy. Varying silicawall thicknesses, asymmetric misalignments of the nested and surrounding cladding elements, and anisotropic deformations are investigated and result in loss increases up to 2%, 6%, and 62%, respectively, for fundamental mode propagation at 1.55 μm. Higher-order modes are affected over one magnitude stronger, although the impact is highly wavelength-dependent, switching dominating effect and mode susceptibility dynamically.

The non-toxic metal halide-based perovskite materials can be a greener alternative to leadbased perovskites because of their stability and high-scale production. Herein, we have tuned the structural and photophysical behaviour of non-toxic halide-based perovskite CsSnCl₃ by forming a heterostructure with reduced graphene oxide (rGO) owing to its high carrier mobility and thermal conductivity. The crystal structure of CsSnCl₃ and CsSnCl₃/rGO heterostructure has been analyzed using the X-ray diffraction (XRD) technique which confirms the formation of a highly crystalline cubic phase. The high absorption behaviour of CsSnCl₃ and CsSnCl3/rGO can be clearly seen from the ultraviolet-visible (UV-vis) spectrum. A direct bandgap of 3.24 eV and 3.19 eV has been calculated from the Tauc plot for CsSnCl₃ and CsSnCl₃/rGO heterostructure respectively. The Photoluminescence (PL) plot shows a high quenching blue shift phenomenon in CsSnCl3/rGO heterostructure as compared to pristine CsSnCl3 material due to the faster separation and transfer of charges from photogenerated electron-hole pairs. Further, the surface morphology of CsSnCl₃ and rGO/CsSnCl₃ heterostructure has been noticed by utilizing the Field Emission Gun-Scanning Electron Microscope (FEG-SEM) representing a very good morphology of synthesized materials in which CsSnCl₃ comprises a granular kind of structure which is spread over the rGO sheet. This study suggests the tenability of structural and optical properties with enhancement in stability of pristine CsSnCl₃ by forming heterostructure with rGO for their future utility in highly stable, and efficient photovoltaic and optical devices.

In this work, the concept of the novel approach called linear alloy capping layer (LACL) has been investigated on the strain-coupled bilayer InAs/GaAs1-ySby QD heterostructures. Here, two analog structures with low (structure BA1) and high (structure BA2) antimony (Sb) contents, and one linear alloyed structure (BL) with varying Sb-content inside the capping layer is considered. The Sb-content inside the CL of structure BA1 and BA2 are 10% and 20%, respectively. Whereas, it is varying linearly from 20% to 10% inside structure BL. The CL and GaAs spacer layer thickness has been taken as 8 nm and 13 nm, respectively. All these three structures have been modeled using Nextnano++ simulation software. Two strain components, hydrostatic and biaxial have been computed and compared. These two strain components help in decreasing the ground state energy gap which leads to a red-shifted PL emission. The structure BL offers improved biaxial strain by 1.11% and 0.56% inside QD compared to structures BA1 and BA2. In addition, the magnitude of hydrostatic strain inside QD of structure BL is reduced by 1.78% and increased by 0.64% compared to structures BA1 and BA2. The strain inside the CL of structure BL is reduced very smoothly in a linear fashion as compared to other analog structures. The computed PL emission of structures BA1, BA2, and BL are 1371 nm, 1665 nm, and 1617 nm, respectively. Also, the proposed structure BL offers a type-II band profile. Hence this proposed approach is useful for future optoelectronic applications.

Rigorous Coupled Wave Analysis (RCWA) method is highly efficient for the simulation of diffraction efficiency and field distribution patterns in periodic structures and textured optoelectronic devices. GPU has been increasingly used in complex scientific problems such as climate simulation and the latest Covid-19 spread model. In this paper, we break down the RCWA simulation problem to key computational steps (eigensystem solution, matrix inversion/multiplication) and investigate speed performance provided by optimized linear algebra GPU libraries in comparison to multithreaded Intel MKL CPU library running on IRIDIS 5 supercomputer (1 NVIDIA v100 GPU and 40 Intel Xeon Gold 6138 cores CPU). Our work shows that GPU outperforms CPU significantly for all required steps. Eigensystem solution becomes 60% faster, Matrix inversion improves with size achieving 8x faster for large matrixes. Most significantly, matrix multiplication becomes 40x faster for small and 5x faster for large matrix sizes.

We propose a Machine Learning (ML) assisted procedure to extract Vertical Cavity Surface Emitting Lasers (VCSELs) parameters from Light-Current (L-I) and S21 curves using a two-step algorithm to ensure high accuracy of the prediction. In the first step, temperature effects are not included and a Deep Neural Network (DNN) is trained on a dataset of 10000 mean-field VCSEL simulations, obtained changing nine temperature-independent parameters. The agent is used to retrieve those parameters from experimental results at a fixed temperature. Secondly, additional nine temperature-dependent parameters are analyzed while keeping as constant the extracted ones and changing the operation temperature. In this way a second dataset of 10000 simulations is created and a new agent in trained to extract those parameters from temperature-dependent L-I and S21 curves.

This article focuses on electro-optical modulators and in particularly it concerns a high efficiency modulator based on a multi-taper coupler. The advantages achieved by adding a modulator located on the multi-taper are: increasing the efficiency, bandwidth, versatility and decreasing the propagation loss while decreasing the connection gate and the location on the PIC, all due to the Multi-Taper coupling sensitivity. Numerical simulations will show the feasibility of changing the coupling efficiency dramatically by a small change on the multi-taper coupler, where coupling efficiency changes dramatically, from 3dB loss up to 38dB loss. The fabrication process will be shown for manufacturing the multi-taper modulator.

Silicon-based Complementary Metal Oxide Semiconductor (CMOS) image sensors are widely used for visible range detection systems. However, when it comes to near-infrared-range (NIR) applications like face recognition or Augmented/Virtual Reality (AR/VR), these sensors are much less efficient. This is due to the poor absorption of Silicon at such wavelengths. A well-known solution studied in-depth over the past few years to address this issue consists of etching diffractive structures into the Silicon. The incoming light is therefore diffracted inside the photodiode, increasing the optical path, and thus improving the Quantum Efficiency (QE) of the pixel. However, the Modulation Transfer Function (MTF) of the sensor is degraded in return on account of the increased light flux crossing from one pixel to the other, being eventually absorbed in the wrong pixel, an optical crosstalk that ends up degrading the MTF. Here, using Finite Difference Time Domain (FDTD) simulations of precisely the same Slanted Edge method as used in MTF characterization, we positively evaluate a new methodology to simulate the MTF of the sensor. We compared simulated results with characterization ones on actual pixels in several distinct configurations. We studied sensors’ MTF without any diffractive structures and others with various structures designed to influence the MTF more specifically in one direction (horizontal or vertical) at 940 nm. We demonstrated good agreements between simulations and characterizations, showing highly correlated tendencies across the whole studied set and giving us parameter predictive power on the MTF for future innovative pixel designs.

Simultaneously prototyping several sensing architectures is costly and time consuming. Therefore, a modeling pipeline that is capable of both nanoscale electromagnetic wave and macroscale ray tracing simulations for the design, performance prediction, and validation of future AR/VR/MR sensing modalities is crucial. However, current end-to-end sensor modeling pipelines use several software packages with cumbersome interfaces between scene radiometry definition, macro optical component design, and photonics component design. In our paper, we demonstrate, implement and validate a sensor modeling pipeline with streamlined interfaces and modular component definition capabilities. The pipeline is composed of Ansys Speos for source radiometry and geometry definition, Zemax OpticStudio for camera lens system definition, and Lumerical FDTD for image sensor definition. This end-to-end pipeline is used to model a camera system developed at Reality Labs and designed for AR/VR/MR applications. The first section of this paper describes the camera system modeled in the pipeline. Validation efforts for the pipeline involved comparing simulated images, obtained from inverse Monte Carlo ray propagation simulations, to experimentally collected images with the corresponding hardware. Specifically, the distortion and modulation transfer function (MTF) were determined for the simulated and experimentally collected images using ImaTest image quality software. The second section of this paper describes these validation efforts and the obtained results. The modularity of the modeling pipeline is highlighted throughout the paper for its applicability to various sensing architectures of interest to AR/VR/MR technologies.