Physics and Simulation of Optoelectronic Devices XXXIII

We propose a monolithically integrated, vertical-cavity nanowire (NW) quantum light source coupled to a silicon (Si) quantum photonic integrated circuit (QPIC). Starting from modelling of the coupling efficiencies of an embedded quantum emitter and its dependencies on key geometrical parameters of NW/Si-waveguide dimensions, we further show experimental progress towards such a deterministic quantum light source using InGaAs emitters in a GaAs(Sb) NW cavity. Key understanding of the growth and optical properties of the InGaAs emitter is provided from systematic structure-property relationship studies.

Several methods have been proposed for interpolation of the value of physical parameters of quaternary alloys from those of their constituent sub-alloys. These expressions agree when non-linear bowing terms are not required; they differ in how the bowing terms of the bounding ternaries should be utilized. Common interpolation expressions for quaternaries can be generalized into two groups: 1) those that use a linear interpolation of the nearest ternary parameter values and 2) those that interpolate over binary values with a bowing term derived from the bounding ternaries. The second group of methods is equivalent to a polynomial expansion over the alloy's interpolation space. A general polynomial expansion of the value of an alloy parameter is described for alloys with arbitrary numbers of elements, including quinary and senary alloys.

Atom probe tomography is combined with finite element method to uncover the in situ electronic and optical properties of an epitaxial InAs/GaAs(001) quantum dot ensemble. The simulated eigenstates demonstrate a high degree of in-plane hybridization across multiple quantum dots, forming complex orbitals that contrast the classical view of quantum dots as isolated objects. This work has important applications in quantum dot laser design through the engineering of ensemble effects.

The potassium tantalate niobate (KTN) crystal, a type of electro-optic crystal, exhibits a relative dielectric constant exceeding 10,000, enabling phase modulation proportional to the square of the electric field through the Kerr effect. On the other hand, due to the high relative dielectric constant of KTN crystals, the in-plane electric field distribution of the electrode patterns causes crosstalk between electrodes. In this study, we utilized multi-physics simulation environment software (COMSOL Multiphysics) based on the finite element method to construct the simulation of the electric field distribution and wave propagation in KTN bulk crystals with comb-shaped electrodes. This report presents the COMSOL Multiphysics simulation results and discusses the effect of geometric structures and electro-optic properties on spatial light modulation.

We have proposed a perfect numerically graphene metasurface based highly efficient tunable C-shaped solar absorber in the frequency range from 10 THz to 1200 THz. The periodically arranged C-shaped in the 3x3 matrix multiple graphene strips placed above top the dielectric layer helps to absorb incoming electromagnetic radiation and increasing highly absorption. The graphene metasurface absorber is designed by sandwich graphene layer sheet between dielectric layer Tungsten and resonator layer Silicon. The Graphene based C- shaped solar absorber is design analyzed in terms of absorption characteristic gives broadband average absorption with 84.7% in infrared (280 THz to 380THz), 89.7% (430 THz to 770 THz) in the visible and 96% in ultraviolet (780 THz to 1000 THz) regions. The band of absorption and reflection varies from lower to higher in terahertz frequency range and vice-versa by changing the design parameters of dielectric layer Tungsten height (H), Silicon resonator height (T). The proposed based absorber design wiil be applicable in Graphene based sensors, optoelectronics devices, photovoltaic devices and energy harvesting devices.

Photonic crystal surface-emitting lasers (PCSELs) are a new type of semiconductor laser design which features in-plane optical feedback from photonic crystal (PC) resonances. The lasing mode in a PCSEL cavity can be designed to operate at the Γ point of momentum space, and an upward emission with low beam divergence can be formed. Such orthogonal electrical injection and optical feedback design offers huge freedom of optical cavity design. On the one hand, high-power continuous-wave (CW) PCSELs with power exceeding 50 W and brightness over 1 GW cm−2 sr−1 have been demonstrated from a 3mm diameter single aperture PCSEL device. To support the development of this new type of semiconductor lasers, coupled electrical/optical designs are considered for high power single mode PCSELs. The impact of the optical lattice and suppression of higher order mode is critical in maintaining single mode operation for large aperture PCSELs. The incorporation of heterostructure photonic crystal cavities can lead to the control of in-plane cavity loss and the coupling of PCSEL arrays. Optimization of heterostructures will also be discussed for the optimal carrier injection and mode selection.

It is typical to manufacture photonic crystal surface emitting laser (PCSEL) devices with contact area smaller than the photonic crystal (PC) defined area in order to maximise power conversion efficiency (PCE). Here we simulate PCSELs with unpumped PC boundary regions. We note that on increasing the size of the unpumped PC perimeter that total parasitic loss (αi + α//) does not reduce to that of αi alone. In this case the internal loss is a function of QW number, PCSEL-gain peak detuning, and pumped and un-pumped size as compared to the PC scattering coefficients. For intermediate cases, we determine the optimal PC matrix size for a given contact size, PC scattering coefficients, and QW number, and predict the modified value for the internal loss, including self-absorption. Impacts on PCSEL design and characterisation will be discussed at the conference.

Nanowire based honeycomb pattern Photonic Crystal Surface Emitting Lasers (PCSELs) have potential of realizing lower threshold devices compared to nanowire PCSELs made of other patterns. This is because it has more degrees of freedom in tuning the design parameters, which isn’t possible in other patterns. Triangular and square pattern nanowire PCSELs with respective lasing thresholds of 130 kW/{cm}^2 and 7\ kW/{cm}^2 have been reported. On the other hand the honey comb PCSEL with threshold of 6.25 W/{cm}^2 corresponding to simulated Q-factor of 5.84X{10}^5 has been demonstrated. This work investigates increasing the Q-factor by deforming the honeycomb pattern and tuning the height and the lattice constant of the nanowires. We simulate and establish the optimum design of devices operating around 960nm, in the O and C bands with quality factors up to 7X{10}^7. This work paves way for fabrication of high Q-factor, nanowire based honey comb PCSELs with low lasing threshold.

A linear analysis of the stability of two modes of generation in semiconductor quantum well lasers is discussed. These modes correspond to two solutions of the set of rate equations obtained by taking into account the internal optical loss that depends on the density of charge carriers injected into the laser waveguide region and, hence, on the injection current. It is shown that, in contrast to the first (“conventional”) mode of generation, which is always stable and hence observable, the second (“additional”) mode, which is entirely due to the internal loss that depends on the carrier density, is unstable and hence cannot be observed under the steady-state conditions in the laser structure considered in this work. Despite the fact that the second mode of generation is unstable and cannot be observed under steady-state (continuous-wave) conditions, its existence can manifest itself under pulsed pumping at high current densities.

Plasmonic nanostructures have the potential to provide breakthroughs in infrared sensing. Multiphysics TCAD simulations of plasmonic cavities coupled to submicron mid-infrared HgCdTe absorbers promise detectivities more than twofold larger than those provided by conventional 5 micrometers-thick absorbers, with comparable responsivity, reducing to one fourth the dark current, hence enabling operating temperatures up to 260 K, broadening the optical spectral response, and leading to higher frequency response. Thin HgCdTe plasmonic cavities are expected to provide good electro-optical performance near room temperature, according to our predictions. Using Peltier cells instead of conventional cooling systems would therefore be of great interest from an experimental and industrial perspective.

Precise detection of greenhouse gases (GHG) is crucial for understanding their sources and trends of emission and developing mitigation strategies. The narrow bandgap of InSb allows it to be sensitive to IR radiation in the MWIR range (3-5 µm) and ideal for detecting gases like carbon dioxide (CO₂) and methane (CH₄), which have absorption peaks around 4.2 µm and 3.3 µm, respectively. We propose a ‘GHG plasmonic meta-absorber’ device that specifically targets fingerprint absorption peaks of CO₂ and CH₄ respectively. Our opto-electrical co-simulations show that the designed Au plasmonic grating over sub-micron InSb film achieves unity absorption at designed wavelengths with 6-fold and 10-fold improvement in photocurrent at 3.3 µm and 4.2 µm wavelengths, respectively. Thus, the proposed plasmonic grating serves a dual purpose: absorption enhancement of MWIR light inside the InSb layer and collecting more current through photoexcited carriers via multiple Schottky contacts.

This work presents the first proof of Si1-xSnx alloy-based split-gate field-effect phototransistors on the Si platform. The device exhibits extremely high responsivity of 6×〖10〗^6 A/W at λ = 850 nm with an incident optical power of 50 nW and fixed Sn concentration of 30%. The obtained responsivity value is the highest among earlier reported values. Thus, this work opens the path for the development of novel high-performance detectors for NIR applications.

We investigate the radiation from a circular annular electron beam coaxially moving inside a dielectric cylinder immersed in a homogeneous medium. By using the electromagnetic field Green tensor the electric and magnetic fields are found inside and outside the cylinder for the general case of dispersion of exterior and interior dielectric permittivities. The energy losses of the beam are studied. Different types of radiations emitted by the beam are discussed. They include the Cherenkov radiation in the exterior medium, the radiation on guiding modes of the dielectric cylinder and radiation of surface polaritons confined on a cylindrical interface. The latter types of waves are radiated in the spectral range where the real parts of the dielectric permittivities of the cylinder and surrounding medium have opposite signs. Numerical results for the spectral distribution of the radiated energy are presented for the Drude model of dielectric permittivity.

There is a desire for single photon avalanche diodes (SPADs) capable of detecting light in the SWIR wavelength range for Lidar systems to increase their range while maintaining eye safety. It is also desirable for these SPADs to be CMOS compatible. Ge-on-Si SPADs have been demonstrated by several groups, but Ge only extends the wavelength response to around 1.6 µm. This paper investigates the design of SPADs using GeSn as an absorber to increase the wavelength response to 2 µm. We will compare the use of Si and Ge as a material for the multiplication region.

We will present an experimentally verified model for characterizing the behavior of single photon avalanche diodes (SPADs) and silicon photomultipliers (SiPMs). This work has been performed in the context of understanding large-scale, next generation physics experiments utilizing a large number of SiPMs. Measurements have been taken under illumination from the UV to the NIR at various bias voltages, angles of incidence and temperatures. This permits a detailed description of optical transmission into the device, the internal structure, and the probabilities of charge carriers producing an avalanche in different regions of the device. We will also present novel measurements of the so-called ‘quantum yield’ in silicon, the number of electron-hole pairs produced in an Si crystal per photon. This has been measured for high energy photons below 350nm via a novel SiPM based technique. This quantum yield information is incorporated into the framework for relevant photon energies. This model can aid in assessing detector performance across a range of optical inputs, characterize nuisance parameters such as optical cross-talk and inform the design of new devices with higher efficiency.

This work will present modelling and experimental results for the secondary emission of photons in silicon photomultipliers (SiPMs). These devices are capable of single-photon detection as a single charge carrier can produce an ‘avalanche’ of charge, resulting in a current pulse from the absorption of a single photon. A charge avalanche will itself produce photons, which may trigger secondary ‘crosstalk’ avalanches in other pixels of an SiPM or in other devices within a detector system. The spectrum and number of photons emitted by laser-stimulated avalanches in various SiPMs, including conventional analogue devices and a ‘digital’ SiPM, have been measured. Measurement results will be presented alongside modelling of photon transport through an SiPM structure. This enables generalization to the emission characteristics of a wide range of SPAD and SiPM structures, and the optimized design of detectors with minimal crosstalk noise.

Passive millimeter and terahertz wave imaging has emerged as a promising technique for human security screening and scene surveillance. Owing to the minimal contrast in brightness temperatures between the human body and concealed objects, enhancing the temperature sensitivity and spatial resolution of radiometers remains a challenging task. The measure of system sensitivity is noise equivalent temperature difference (NEΔT) and probability of detection (Pd). While conventional RF receivers down-convert the received signal using a mixer and local oscillator for image rendering, herein we present the latest developments of a state-of-the-art optical up-conversion receiver that up-converts the received RF signal onto the sideband of an optical carrier across a phased array antenna. After up-conversion, each signal is routed back to an optical fiber bundle that is subsequently spatially Fourier transformed using a lens, to render an image. In this presentation, a theoretical study and system level simulations are used to illustrate the efficacy of this approach, in terms Pd.

Metalenses have the potential to revolutionize optical products for compact imaging, sensing, and display applications. However, this emerging technology faces significant challenges in both design and manufacturing. The design difficulty arises from the vastly different length scales involved: the macro scale of the lenses (macro-optics) and the micro scale of the constituent meta-atoms (micro-structures). The manufacturing complexity stems from fabrication errors associated with these micro-structures, which can lead to unintended deviations from the intended design. To address these challenges, we have developed a fully automated design flow that integrates ray optics and wave optics for complex optical designs, such as hybrid refractive-metalens systems. To account for and mitigate manufacturing impacts during the design stage, we have created a virtual fabrication environment through process simulation. By using manufacturing-aware meta atom libraries from the outset, rather than ideal meta-atoms, we ensure that the initial fabrication run can meet the intended design specifications.

Stray light analysis is crucial to mitigate the contribution from unwanted light and addressing image quality issues in high-quality optical systems. Traditional simulation approaches to analyze stray light can be time-consuming. It is also important to evaluate the contribution of stray light within the final application environment. In this paper, we describe how you can evaluate the image quality of a camera system with an acceptable simulation time considering the impact of stray light coming from reflections on lens, mechanical components and imager for a cellphone camera in a landscape with sunlight. We are highlighting the seamless integration between simulation tools and simulation efficiency leveraging GPU computation and converging method.

When calculating the near-to-far-field (NTFF), we need to select a virtual surface. However, in the finite-difference time-domain (FDTD) method, the electric field and magnetic field are misaligned in space. Therefore, if the electric field is used for far-field calculations, the magnetic field must be obtained by the averaging method. We use collocating to average the magnetic field and compare it with non-collocating. We expect that the result of collocating will be more accurate when the far-field values are at a lower resolution (lower dB).

A photonic crystal is a structure in which dielectrics are periodically arranged in space. In the two-dimensional photonic crystal, we designed line defects to form a waveguide structure. The propagation of electromagnetic waves in line defect structures with different bending angles is simulated through FDTD, and its penetration is analyzed. We obtain the penetration rates under different bending angle structures. Going further, explore how to improve the structural design to achieve optimized waveguides with different angle structures. In integrated optics, the bending loss of waveguides is a very important issue. Through this simulation study, we can understand the impact of different degrees of bending angles on the loss of light transmission.

In this work, we explore excitonic properties and exciton-phonon interactions in atomically thin nitrides, highlighting their potential for optoelectronic and excitonic devices. First, we investigate atomically thin GaN quantum wells, just a few atomic layers thick, encapsulated within Al(Ga)N barriers. The strong confinement in these quantum heterostructures significantly increases the bandgap, enabling deep-UV emission and enhancing exciton binding energy, improving radiative efficiency. Second, we examine how strong exciton binding and exciton-phonon coupling in bulk h-BN enable efficient deep UV emission, despite its indirect bandgap. We also find that monolayer h-BN on graphite substrate exhibits significant renormalization of its electronic bandgap and exciton binding energy due to strong screening by the graphite substrate. Finally, we present a theoretical framework for phonon screening of excitons to accurately assess exciton binding energy in reduced-dimensional systems. We reveal that in atomically thin semiconductors, vibrational modes confined exclusively to the barrier or substrate region, known as half-space (HS) modes, can greatly influence screening of excitons.

This study employs theoretical analysis to quantify the projected modulation speed of MicroLEDs, comparing N-polar and Ga-polar GaN structures. By calculating the bimolecular radiative recombination coefficient across emission wavelengths and quantum well thicknesses using numerical solutions of the Schrödinger equation for the wavefunction overlap coefficient, we demonstrate that the maximum enhancement occurs at a wavelength of 450 nm, achieving a ninefold increase in the radiative recombination coefficient with N-polar GaN. This improvement translates to an approximately threefold increase in modulation bandwidth, highlighting the significant potential of N-polar GaN in optimizing MicroLED performance for high-speed applications.

AlGaN-based LEDs show promise in deep ultraviolet (DUV) emission for environmental and medical uses, but optimizing carrier injection efficiency (CIE) is challenging. This study uses a microscopic simulation model to investigate the emission spectra of dual wavelength AlGaN LEDs. The model includes advanced features such as carrier transport dynamics, and radiative recombination processes. The simulations examine LEDs with varying quantum wells (QWs) emitting at 233 nm and 250 nm to understand carrier distribution. Results indicate that electron densities in the MQW stack are higher than hole densities, leading to an imbalance that affects CIE and optical spectra.

Thin film interference is essential in optoelectronic devices, impacting all spectral characteristics such as emission, transmission, or absorption profiles. However, photonic systems relying on optical thin films fundamentally face blue shifts at non-normal angles of incidence. We address this issue by utilizing ultra-strong coupling between cavity photons and material excitons, transitioning the photonic to a flat exciton-like dispersion. This technique is especially effective when using organic materials with high oscillator strengths and enables angle-independent, narrowband responses. We demonstrate both narrowband and broadband, angle-independent transmission filters in metallic cavities and are able to generalize this enhanced performance to distributed Bragg reflector-like dielectric stacks. Additionally, we develop polaritonic narrowband photodetectors and organic LEDs [1] with minimal dispersion. This approach benefits micro-optics, biophotonics, and other fields addressing light collimation challenges, demonstrating the practical utility of strong coupling in creating spectrally stable optoelectronic devices. [1] Mischok et al., Nature Photonics 17, 393, (2023)

We present how the frequency degree of freedom of light can be used for neuromorphic computing. Since multiple frequencies can propagate in the same device without interacting, this provides a simple and natural way to exploit the parallelism of photonics in computing. In the works presented the information is encoded in the amplitudes of a frequency comb. Interference between comb lines is realized using electro-optic modulators or the Kerr nonlinearity in an optical fiber. This approach is demonstrated on two rather simple machine learning algorithms, Reservoir Computers and Extreme Learning Machines, both implemented using fibre optics setups. A programmable spectral filter is used to implement the output weights in the optical domain.We also demonstrate how 2 such Reservoir Computers can be combined in a deep architecture, with the interconnection between reservoirs implemented entirely in the analog domain. We discuss the relation to other photonic neuromorphic architectures that exploit the frequency degree of freedom, but in a highly nonlinear regime (typically using femtosecond pulses), as well as the potential for implementation in integrated optics.

Tunnel injection (TI) lasers are an appealing concept for the next generation of semiconductor lasers, as they promise improved modulation rates and better temperature stability. Moreover, they eliminate a major detrimental effect of quantum dot (QDs) lasers, which is the gain nonlinearity caused by hot carriers. In QD-TI lasers, the excited charge carriers are efficiently captured from the bulk states via an injector quantum well and then transferred into the QDs via a tunnel barrier. The introduction of a tunnel barrier for controlling the coupling of QDs to an injector quantum well (QW) introduces significant design changes in comparison to conventional QD or QW lasers. As a result, nanoscale physics and quantum mechanical interaction processes take a more important role in the device properties. We present [1] a theoretical study of dynamical laser properties inclusing the transport within the device and show the impact of alignment between the injector quantum well and the QDs on the laser switch-on process and modulation properties. These are important for the use of these laser systems in novel telecommunication applications. [1] arXiv:2402.18165

We show how dynamic optical injection can be used for rapid and wide tunability of the pulse repetition rate of a mode-locked quantum-dot laser. We harness this capability to demonstrate record scan rates in high-speed optical sampling by cavity tuning (OSCAT) and parallel heterodyne interferometry via rep-rate exchange (PHIRE).

Synchronization of nonlinear dynamics is a concept that is widely encountered in nature and it has been thoroughly explored in domains as varied as biology or mechanical clocks. In the context of lasers subject to optical feedback, most of the studies focus on systems with a limited number of emitters. Our experimental work demonstrates extended synchronization in a large array of blue semiconductor lasers subject to filtered optical feedback. The long-range synchronization among the 12 chaotic emitters in the array is confirmed by temporal correlations in the time series and by frequency locking in the optical spectra of individual lasers.

This paper introduces a photonic architecture that emulates Hebbian learning in biological neural systems. By integrating micro-ring filters, phase change material-based micro-ring modulators, and photodetectors, the system simulates neuronal components like synapses and dendrites. Each Photonic Synapse Block (PSB) operates at distinct wavelengths, allowing for multiple synaptic inputs through serial connections. A microcontroller dynamically adjusts synaptic weights based on neuronal spike patterns, enabling high-speed studies of synaptic dynamics and neural plasticity. The inclusion of PCM enhances the system’s adaptive learning capabilities, crucial for understanding neural behaviors and disorders. This architecture not only accelerates research in neuromorphic photonics but also demonstrates scalability and practicality through an active photonic integrated circuit developed with AIM Photonics. This work represents a significant step toward bridging the gap between theoretical neuromorphic models and their practical applications.

The Optical Phased Array (OPA) is a breakthrough technology for light beam forming and dynamic beam steering, by operating a signal phase control over an array of independent emitters, with no need for mechanical moving components. The full and correct operation of an OPA, requires the satisfaction of a condition over the distance between the emitters to be smaller than half wavelength. At the same time, the short distance between the PIC waveguides causes a pronounced crosstalk between them, reducing the beam quality and the overall system performance. The PECVD characteristic that can be useful for 2D-OPA PIC fabrication is that avoiding thermal diffusion process, it allows the deposition of multilayered structures by a sequential process. Such an OPA design would be capable of producing a well-formed gaussian beam spot, respecting the half wavelength rule in a 2D domain, with reduced secondary lobes formation and allowing a large FOV in both dimensions. This work report about the project and layout design of an amorphous silicon 2D OPA in 16x16 End-Fire configuration. Computer simulation of the single building blocks and the overall device. project IPL/IDI&CA2024/OPAPIC2D_ISEL

Fiber-coupled single-photon sources, which can operate at room temperature, is an essential component for implementing optical quantum communication technologies such as quantum internet and quantum key distribution. Here, we experimentally demonstrated the generation of single photons at room temperature from a single rare-earth(RE) ion isolated in the optical tapered fiber. Our single photon source is fabricated based on commercially available RE ion doped fibers, which can be prepared at low cost. To investigate the characteristics of our single-photon source, several optical properties were also observed such as saturation intensity and fluorescence lifetime. Our results will lead to the realization of various photonic quantum information technologies such as optical quantum communication networks.

In this study, several nanowire shapes are numerically investigated and integrated into different solar cells utilizing lumerical finite difference time domain to determine the generation rate and current density. charge solver is used to examine electrical properties such as short circuit current, open circuit voltage, and power conversion efficiency (PCE). Since the dimensions of the nanowires greatly influence their attributes, this study looks at varying the diameter and length of the nanowires to improve the solar cell's PCE and light absorption to satisfy commercial demands. By optimizing the diameter of flower-shaped nanowire solar cell from earlier research is enhanced, resulting in a 2.2% higher PCE as well as better current density and light absorption, given that the PCE obtained by the literature is 9.6%. The PCE increased to 11.8% with the adjusted diameter. The goal of the ongoing study is to compare various shapes and control the structural parameters to get better performance.

In semiconductor manufacturing, traditional defect inspection methods like TEM are precise but destructive. Through-focus Scanning Optical Microscopy (TSOM) offers a non-destructive alternative by capturing 3D multi-focus patterns. This study enhances TSOM by combining Coupled Mode Theory (CMT) and the Fourier Modal Method (FMM) to overcome computational challenges in large-area simulations. The proposed hybrid technique partitions the structure to calculate coupling coefficients, allowing efficient parallel computation. Validated through simulations, this approach significantly improves defect detection efficiency and precision, making it highly applicable for semiconductor inspection.

In this study, the performance of InAs/GaSb/AlSb superlattice photosensors is investigated using the Multiphysics simulation tool COMSOL. This research focuses on the impact of different quantum well structures on wavelength coverage and photosensor detection efficiency. The study is divided into sections exploring various factors influencing device performance: the effect of quantum well thickness on the detection wavelength range, the impact of varying the number of quantum wells on current density, the influence of the doping concentration and profile on the detection efficiency, and the optimal operating conditions regarding the bias voltage and input power density. For each configuration, the bandgap structure and response curve are calculated using the Finite Element Method, with comparisons made across wavelength ranges and photocurrent densities. This simulation work aims to guide the design and fabrication of high-performance photosensors, offering insights into semiconductor material selection, quantum well optimization, and doping strategies.

We proposed an analytical method to calculate the reflectance of arbitrary guided modes reflected on angled facets of optical waveguides. Our method consists of rotating the electromagnetic field of the incident mode and performing the mode overlap of the incident and reflected one. The main advantage of our method is that the reflectances at tilted interfaces can be calculated for any mode field distribution. We evaluated the reflectances of fundamental modes for transverse electric and magnetic polarizations in niobate lithium waveguides operating at λ = 1.55 µm. The results confirm that the reflectance of the modes is very dependent on the mode field size, in other words, the greater the MFD, the lower the end facet angle needed to achieve low reflectance levels.

This study presents an innovative approach to designing bilayer linear gratings for high-performance mid-wavelength infrared (MWIR) polarimetry using deep learning techniques. We developed an artificial neural network (ANN) model trained on finite element method (FEM) simulations to predict electromagnetic responses of bilayer grating structures. The model demonstrates high efficiency and accuracy in predicting transmission behavior, significantly reducing computational time. We validate ANN predictions through experimental fabrication and characterization of nanoimprinted bilayer gratings. The study identifies critical geometric parameters influencing transverse magnetic and transverse electric transmission, enabling tailored designs for specific MWIR wavelengths. Integration of optimized bilayer grating structures with MWIR InAs/GaSb Type-II Superlattice (T2SL) photodetectors yields significantly enhanced spectral responsivity and polarization sensitivity. Our approach provides a versatile route for rapidly designing and optimizing metamaterials for high-performance polarizers, offering superior capabilities to resolve linear polarization signatures in various applications.

We present new insights into the dynamics and stability of quantum-dot passively mode-locked lasers, with the help of a highly-sensitive dispersion-scan (d-scan) setup, able to provide the full characterization (phase, amplitude) of the picosecond, picojoule pulses emitted by these lasers. The approach used here can be more generally applied to other low-power, picosecond and sub-picosecond lasers and should be of interest for application to a wide range of on-chip, integrated sources of ultrashort pulses.