This PDF file contains the front matter associated with SPIE Proceedings Volume 11995, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

The advantage of mid-infrared wavelength is that it is less affected by atmospheric conditions than conventional near-infrared wavelength, and this optical domain is thus envisioned to play a key role in the 6G standard under development. The directivity of the beam, as well as the stealth conferred by the background emission, makes communication systems based on long-wave infrared quantum cascade lasers (QCL) highly desirable. However, some applications require a further level of privacy. Protecting the communication link against eavesdroppers is possible with chaos-based enciphering. Using this concept, a chaotic master QCL is used to conceal the private message while deciphering is achieved with a second, identical, remote QCL that is called the slave. The deciphering process relies on chaos anti-synchronization where the slave only reproduces the reversed chaotic pattern of the master, thus allowing the recovery of the private message by adding the slave signal and the master signal. The privacy of our system is also assessed and shows that an illegitimate receiver would end with a detrimental error rate during translation, even in the unlikely case this eavesdropper knows the coding format of the private message. We believe our private communication system brings a cost-effective, reliable and versatile alternative for free-space data links, especially in harsh environments where mid-infrared lasers strongly outperform their near-infrared counterparts. Features such as room-temperature operation and highspeed transmission further advocates for a large deployment, and we anticipate that this finding can have a significant impact on the development of novel applications based on QCLs.

The impact of optical feedback on the emission properties of edge-emitting diode lasers is crucial for their use in various applications with unavoidable optical feedback. A hybrid master oscillator power amplifier (MOPA) concept based on a low-power laser (MO) and a tapered amplifier (TPA) is well suited for those applications. The MOPA offers the ability to mechanically separate the MO from the TPA, which allows to shield the MO against possible optical feedback from the TPA by using an optical isolator. However, the feedback emitted from the TPA towards the MO has not been investigated in detail yet. In addition to the feedback from the TPA the MOPA as a whole can be subject to external feedback. Depending on the beam path in the respective application, feedback ratios in the range from 10⁻⁴ to 10⁻² to the TPA may occur. The optical feedback coupled to the TPA is expected to be also amplified in the TPA which increases the feedback towards the MO dramatically. Therefore, the propagation of feedback light through the TPA and its emission characteristics towards the MO have to be studied in detail. A beam propagation method including a model for the charge carriers and a fast thermal solver utilizing a Green’s function approach is used to simulate feedback propagation inside the TPA. A description of the model, with focus on the thermal solver, will be presented as well as a comparison to measurements. The results allow to optimize MOPAs with respect to feedback more accurately.

Gas sensing based on modulation spectroscopy requires sinusoidal modulation of the laser sources. This work proposes a modulation scheme for quantum cascade lasers, using the period-one (P1) oscillations. The P1 oscillations are introduced by the tilted optical feedback. Although the optical linewidth of the laser is around 15.0 MHz, the beat-note electrical linewidth of the modulation is less than 2.0 kHz, which suggests that the optical sidebands induced by the P1 oscillations are highly coherent with the main optical mode. In addition, the modulation frequency can be simply tunned by adjusting the feedback length, and the modulation depth of the optical signal is in the range of 1.0 % to 3.0 %. In contrast to the direct modulation scheme and the external modulation scheme, the proposed P1 modulation method does not require any radio-frequency electronics.

In this work, we report postmortem studies in shock compressed direct band-gap semiconductor crystals. Commercial III-V wafers were characterized before and after dynamically compressing them using a laser driven flyer plate system (LDFPS), developed and characterized in the recent years by the Dlott research group. LDFPS is an inverted shock microscope with high time and space resolutions, and is suitable for high-throughput shock compression experiments. The postmortem characterization in recovered samples via x-ray diffraction, photoluminescence, and Raman measurements showed evidence of permanent alterations in the crystal structures of the compressed materials. Considering the wide usage of semiconductor bulk substrates in the hi-tech industry, we note the significance of practical, pressure-induced band structure engineering pathways.

In this paper, the impact of variation in the number of quantum wells and barrier layers on optical properties of GaN/AlGaN based light-emitting diode (LED) is investigated while keeping the width of the active region constant. The number of quantum well and barrier layers are varied from one to six. Simulations are carried out in TCAD software and it is observed that output optical power first increases to a certain number of quantum well layers in the LED and beyond it there is no significant increase in the output power. Output power is increased by 44% when the quantum well layer increases from three to four, thereafter it starts decreasing. On the other hand, the maximum intensity of light continuously decreases with an increase in the number of quantum well layers. The number of layers after which the optical power saturates or decreases is device-specific.

Interfacing semiconductor with photonic qubits plays an important role in quantum networks. We model a photon to spin qubit interface based on an optically active gate-defined quantum dot embedded in a two-dimensional photonic crystal cavity constraining its emission profile with a low enough quality factor for emission wavelength tuning. By matching the cavity-mode k-vector and reciprocal lattice of the crystal, vertical emission is obtained. A reflector below the cavity increases not only the light extraction efficiency, but also tailors the extracted beam profile to match that of a single mode fiber, into which photons emitted by the quantum dot are coupled with a probability above 50%. The efficiency is primarily limited by metal electrode absorption. In addition to trapping the exciton, the electrode system embedded inside the cavity allows trapping, manipulation and readout of a pair of electrons encoding a spin qubit in a singlet-triplet configuration, whose quantum state can be transferred to and from the exciton by utilizing an existing protocol. Experimental realization of these devices is currently in progress with first results in regard to fabrication also reported.

Vast improvements in communications technology are possible if the conversion of digital information from optical to electric and back can be removed. Plasmonic devices offer one solution due to optical computing’s potential for increased bandwidth, which would enable increased throughput and enhanced security. Plasmonic devices have small footprints and interface with electronics easily, but these potential improvements are offset by the large device footprints of conventional signal regeneration schemes, since surface plasmon polaritons (SPPs) are incredibly lossy. As such, there is a need for novel regeneration schemes. The continuous, uniform, and unambiguous digital information encoding method is phase-shift-keying (PSK), so we chose to focus on developing a regeneration scheme compatible with PSK. Epsilon-near-zero (ENZ) materials have been shown to support SPP modes and have extremely high conversion rates for harmonic generation at their zero-permittivity wavelength, which makes them particularly desirable for developing signal regeneration devices. We have shown second-harmonic generation (SHG) in free space with simulations consisting of ENZ materials. When integrated into plasmonic waveguides, SHG can be used to conduct phase sensitive amplification (PSA), which allows us to combine phase-squeezing and amplification into a single stage instead of relying on conventional gain media for amplification. PSA can be utilized to design a proof-of-concept signal regeneration device with a smaller overall device footprint than previously demonstrated methods. The development of these methods will contribute towards minimizing device footprints of plasmonic components that require signal regeneration, improving their density and performance.

Coupling light into or out of a photonic integrated circuit is often accomplished by establishing a vertical link between a single mode optical fibre and a resonant waveguide grating, which is then followed by a tapered and a single mode waveguides. For a chip to fibre coupler, the period of the diffraction grating is often apodized to achieve an optimal beam profile at the input of the optical fibre. The tapered waveguide operates as a spot-size converter, expanding laterally the light beam in the single mode waveguide, to match the profile of the fundamental mode of the resonant waveguide grating. In this work, we propose using subwavelength structures to modulate the refractive index of the tapered waveguide for the lateral expansion of the light beam, when operating at the 1550 nm wavelength. The engineered graded index structure is simulated through adequate numerical methods and its performance is analysed in terms of efficiency and mode profile matching. With our proposed inverted taper waveguide, we were able to obtain an adiabatic power transfer and coupling efficiency with the TE fundamental mode of -0.26 dB and -0.92 dB, respectively. This performance has been achieved in a structure 11.1 μm long and 14.27 μm wide. Furthermore, the obtained fields were fed into a resonant waveguide grating to evaluate the coupling efficiency into the fundamental mode of an optical fibre, resulting in an expected performance decrease of 0.1 dB and ~0.6 dB by comparing respectively with the power transfer and coupling efficiency of the resonant waveguide grating when propagating the calculated TE₀ mode.

We present an electrical and optical model for simulating the current distribution in and the resonant light emission from nanostructured organic light-emitting diodes (OLEDs). A periodic nanostructure in an OLED can be used as a resonant waveguide grating to tailor the light emission, i.e., to direct the dominant emission wavelength into a specific direction. We show that the current injection at nanostructured electrodes is strongly enhanced at their corners, leading to localized current paths and emission zones. These current paths have to be overlapping with the resonant optical field hot spots in order to gain maximal resonant light outcoupling. We show that this is not generally the case for periodically nanostructured OLEDs and that the introduction of local isolation layers can improve the overlap by altering the current paths. Depending on the isolation layer configuration either the resonant or non-resonant light outcoupling is pronounced. This optimization potential may be beneficial for compact organic optoelectronic sensors that require highly directional OLED emission.

Group IV-based optoelectronic devices have been intensively pursued to enable full monolithic Si photonics integration. Such devices have great potential for future needs of compact, low cost, and high -performance. Since group IV semiconductors are inhibited from efficient light emitters due to their indirect bandgap nature, a novel group IV material system, GeSn alloy, has attracted renewed interest. GeSn alloy yields true direct bandgap with Sn incorporation over 8%, and it can be monolithically grown on Si making it desirable for developing a Si-based light source with fully complementary metal-oxide-semiconductor (CMOS) compatibility. Over the past few years, considerable progress has been reported on the development of optically pumped GeSn lasers based on direct bandgap GeSn alloys, f ollowed by the recent demonstration of electrically injected GeSn lasers. In this work, we report the development of electrically injected GeSn laser diodes utilizing GeSn/SiGeSn heterostructures grown on Si substrate, with detailed attention given to the cap layer to reduce the optical loss. The material was fabricated into ridge waveguide laser devices and lasing performance was investigated under pulsed conditions. The collected electroluminescence signa l shows clea r la sing signature, and the L−I characteristics of devices with different cavity lengths were studied at various temperatures. The results provide a route for the improvement of high-performance electrically injected GeSn laser diodes.

On-chip integration of semiconductor lasers have shown a growing interest in recent years, especially for the development of photonic integrated circuits (PICs) which are of paramount importance for high-speed communication within and between data centers, and fast on-board data exchanges. For all these applications, a key challenge remains the stability of the laser sources integrated on a PIC in presence of external optical feedback with the view to avoid integrated bulky and costly optical isolation. In this study, the effects of external optical feedback are investigated in hybrid InAs/InP quantum dot comb lasers on silicon. The design of the cavity includes a semiconductor optical amplifier section, a saturable absorber and an on-chip external cavity incorporating a vertical coupler. We measured the resulting feedback properties with respect to the operation conditions (bias current and voltage) and to the length of the saturable absorber. We show that under most operating conditions, the laser remains stable against optical feedback, only few regimes of operation occur, which either improve or degrade the frequency comb and/or the radio-frequency beatnote power of the laser.

While silicon photonics is considered as the key technology for future applications in optical transceivers, ASICs and sensing devices, there are still challenges to achieve generalized mass production of Photonic Integrated Circuits (PICs). One obstacle is the required extreme miniaturization of the photonic devices. Nevertheless, there is space for applications with equal interest and impact in the society that do not require the extreme performance associated with PICs built on a tenth of nanometer scale. Low-cost PICs can be obtained by increasing the size of the waveguides and devices to a multi-micron scale and in this case the machinery necessary for the device fabrication can be greatly simplified. The transfer of the amorphous silicon (a-Si:H) production technology developed in the past for the photovoltaic and flat panel displays can be adapted to the production of multi-micron size PICs targeting low-cost devices working with low frequency signals. To enable the use of such devices it is important to show that light and be coupled in and out of the waveguides efficiently without the need for diffraction gratings or other components that require sub-micron fabrication resolutions. In this article we perform simulation of the power transfer between a lensed 19.4 µm multimode optical fiber and a multi-micron a-Si:H rib waveguide, designed to support single-mode propagation. Light coupling efficiency is analyzed as a function of alignment and distance variations using the FDTD and the Beam Propagation methods. Results show a fundamental TM mode overlap over 80 % under optimal alignment conditions.

Growing demands in high data capacity and low energy consumption have driven the development of high-performance optical interconnects for many commercial applications, such as links for long-haul, intra-/inter-datacenter, and 5G communication. Typically, the photonic devices used in these environments are optimized for operation at or above room temperature, however there is an existing and growing need for optimized photonic devices to operate in cryogenic and/or high-radiation environments. Applications of these optical interconnects range from control and readout from superconducting integrated circuits for quantum computing, to readout of tracking detectors in high-energy physics (HEP) particle accelerators, to readout of next-generation infrared (IR) focal plane array (FPA) detectors. Key to the success of these optical interconnects is the high-performance and ruggedization of the electro-optic modulator (EOM), typically implemented either as a remoted external device or as a directly modulated light source. The underlying semiconductor physics models of the EOM must account for the conditions presented by the harsh environment, leading to optimization challenges at both device and link levels. The current state of the art of optical interconnects for harsh environments will be reviewed, highlighting the current challenges and opportunities, in addition to presenting an outlook on the technology development trends and enabling applications.

Diffraction gratings are among the essential devices for spreading and shaping beams in a wide range of optoelectronic and photonic sensors and fiber optic communications. This has triggered an interest towards inverse design and optimization of the parameters using gradient-based optimization, heuristic algorithms, and machine learning models. Approaches based on complex models (such as deep neural networks) provide enhanced robustness and rely on a huge amount of data to achieve accuracy. However, the generation of these data and multi-parameter optimization can be laborious and time-consuming with the Finite Difference Time Domain (FDTD) simulation. We present an optimization approach to obtain a single grating antenna with wide-angle emission for a photonic integrated flash Light Detection And Ranging (LIDAR) system. The device is simulated using a silicon nitride material operating at a wavelength of 905 nm. Our method relies on a supervised, data-centric approach in combination with a genetic algorithm optimization. Given an optimization and several parameters, we evaluate the variables based on their correlation with the merit function and reduce the search region consequently. This approach allows faster convergence and provides a flat field of view of (56.95°, 92.82°) at Full Width Half Maximum (FWHM) in one dimension simulation.

Understanding the interactions between light and small samples at the diffraction limit is critical for solving inverse problems in microscopy. Several models for light and matter interactions have been proposed, including Born and Rytov approximations, Mie theory, T-matrix, Finite element methods, and coupled wave theory. Coupled wave approaches provide unique advantages for realistic samples by allowing refinement of the sample in the Fourier domain, where many realistic samples are considered sparse. However, this model still relies on computationally intensive operations as the sample and field resolution increases. In this paper, we develop an optimized open-source tool using established coupled-wave theory. This can be computationally efficient for realistic problems, since many practical samples are sparse in the Fourier domain. Then we analyze the computational complexity of the model and optimize the process.

Broadband and omnidirectional anti-reflection coatings, Distributed Bragg Reflectors (DBR), and optical bandpass filter coatings in the 3-5 μm and 1-12 μm IR ranges are of crucial importance in the design of high-efficiency MWIR / LWIR detectors, Thermophotovoltaic devices, and IR imaging systems. We discuss a novel inverse design approach to multilayer optical coatings by a Transfer Matrix Method simulation and optimization algorithm. This algorithm iteratively simulates a multilayer structure's reflection and transmission characteristics by the Transfer Matrix Method and updates layer thicknesses to optimize a performance metric – whether reflection, transmission, or filter performance – over a given band and range of angles of incidence. The optimization procedure provides a systematic, computational approach to designing optical coatings with desired reflection, transmission, and absorption characteristics over wavelength bands and angles of incidence of interest in an application. We show that Distributed Bragg Reflectors and Anti-reflection coatings generated by the algorithm outperform conventional quarter-wavelength layer coatings over broadband MWIR and LWIR ranges and angles of incidence as high as 70 degrees, while reducing total component thickness significantly – a major benefit when fabricating optical coatings on semiconducting substrates directly. We also discuss how the approach can be extended to sharp-cutoff broadband bandpass filter design.

In this study, gain-switching characteristics of InAs-InP(113)B quantum dot laser based on multi-mode rate equations are investigated for the first time by applying an external Gaussian pulse beam into the excited state to obtain short pulses. The rate equations including nonlinear gain are solved for direct relaxation model by 4th order Runga-Kutta method. The obtained results demonstrated that width of gain-switching output pulses are long due to dominant effect of ground state photons having long width without optical beam. Furthermore, pulse width increases with the increasing the peak injection current was observed. However, it was found that since excited state photons have narrow width compared to that of ground state, width of output pulses decreases giving a pulse width of around 25 ps owing to dominant effect of excited state with the applying optic beam into excited state. Our results also indicated that differential-gain of excited and groundstates decreases with the increasing of the homogeneous and inhomogeneous broadenings.

We present an avalanche photodetector (APD) behavioral modeling methodology for Silicon Photonics process design kit. The proposed APD behavioral model can describe nonlinearity of multiplication factors versus both bias voltage and input optical power, and it can also cover process-voltage-temperature (PVT) variations. Inside the APD model, built-in lookup tables that contain multiple coefficients are implemented, therefore nonlinear multiplication factor curves can be easily calculated with an automated coefficient setting algorithm which helps to streamline the verification process and reduce model parameter setting time without sacrificing accuracy. Specifically, as coefficients are derived from different PVT conditions, the proposed APD behavioral model has wide verification coverage.

In this paper we propose a multi-periods composite dielectric film which can reflect infrared and near-infrared light and permit for transmission of visible light. A theory framework is derived to model the transmission and reflection of the composite dielectric film. The results show that the larger the period, the longer the central wavelength of the reflection spectrum. When glass films with multiple period constant composites are used, the wider the reflection spectrum coverage is for films with more period types.

In this study, we minimize the strain by using the new technique called linear alloy technique (LAT) for the Stranski-Krastanov (SK) quantum dot heterostructure. Here, three different SK InAs QDs heterostructures with 6 nm thick capping layer (CL) having In_xGa_1-xAs as capping material have been simulated using the 8-band k.p. model-based Nextnano software. Here, the first sample is analog alloyed SK QDs heterostructure having In_0.15Ga_0.85As capping (Sample A1), the second sample is digital alloyed SK QDs heterostructure where CL is divided into three sub-layers each of 2nm thickness with indium composition varied from 45-30-15% (Sample D1), and the third sample is linear alloyed SK QDs heterostructure where indium composition is varied from 45% to 15% (Sample L1) in a linear fashion, have been studied. The biaxial and hydrostatic strain is computed for all three heterostructures and compared. The biaxial strain is improved by 2.03% and 2.0%, and hydrostatic strain is reduced by 3.49% and 0.071% inside the QD region of sample L1 compared with samples A1 and D1, respectively. Additionally, digital sample D1 offers a step-wise strain reduction inside CL compared to analog sample A1. However, sample L1 offers an even more relaxed strain inside CL than samples A1 and D1, respectively. The PL emission wavelength is observed at 1317, 1372, and 1379 nm for samples A1, D1, and L1, respectively. Hence the linear alloy technique is useful for making future optoelectronic devices where strain reduction is the main factor.

In this study, variation in Sb composition in In0.18Ga0.82AsYSb1-Y as capping layer (CL) over SK QDs and matrix material (MM) in 6 stacks of SML QDs for InAs SML, and strain coupled InAs SK-on-SML QDs heterostructure have been done theoretically. The structural and optical properties have been investigated through Nextnano++ software. Different single-layer SK (A-series), SML (B-series), and coupled SK-on-SML QDs (C-series) structures have been modeled for this study. Two main strain components, hydrostatic and biaxial strain have been computed simultaneously with the solution of 3-D Schrodinger’s equation. The hydrostatic strain is compressive in the growth direction and gives information about carrier confinement in the conduction band while a biaxial strain is tensile in the growth direction and gives information about splitting in the valance band. There is a significant improvement of hydrostatic and biaxial strain observed for A-series and B-series structures respectively, which have quaternary capping, which helps in reduced overall strain and reduced InAs QDs desorption. In Addition to that, the coupled SK-on-SML structures (C-series) with InGaAsSb (Sb-15 and 25%) as capping layer and matrix layer possess more biaxial strain and reduced hydrostatic strain as compared to the conventional coupled structures with InGaAs as matrix material of SML and GaAs as capping layer over SK. The computed PL emission wavelength for proposed C-series structures offers a red-shift over conventional coupled structures. These configurations show type-II band alignment which can be used for various optoelectronic applications in the SWIR regime such as solar cells, long-range communication, etc. This study can be advantageous for the optimization of strain-coupled heterostructures.

Metallic nanowire arrays have been used for discriminating linear polarization and used as a wire-grid polarizer in the simplest form. For their linear geometry, metallic nanowire arrays distinguish p- (perpendicular) from s-polarization (parallel) with respect to the direction of nanowire arrays. In this study, we analyze opto-thermal response on metallic nanowire arrays, for which we performed simulation using finite element method to solve wave-coupled heat transfer equations on metallic nanowire arrays. From the analysis, it was shown that s-polarized light presents lower maximum temperature T_max = 331.7 K than that of p-polarized light T_max = 354.5 K under an incident power at 0.1 mW/μm². In addition, thermal extinction which is defined as the ratio of maximum temperature between p- and s-polarization is measured as 4.78 dB which corresponds to a temperature difference of 54.3K. We have also investigated dispersive misregistration assuming that metallic nanowire arrays are integrated with an imaging detector placed at the focal length of a tube lens. The dispersive effect of a convex tube lens was evaluated using non-uniformity metrics that measure offaxis performance (NTr_off, ER_off) and wavelength dependence (NTr_λ, NER_λ). Maximum non-uniformity was measured to be NTr_λ.max = 0.84935, NER_λ.max = 0.90139, NTr_off.max = 0.93211, and NER_off.max = 0.93624. Image misregistration induced by dispersive effects was also assessed.

Vanadium dioxide (VO₂) as a phase-change material controls the transferred heat during phase transition process between metal and insulator states. At temperature above 68°C, the rutile structure VO₂ keeps the heat out and increases the IR radiation reflectivity, while at the lower temperature the monoclinic structure VO₂ acts as the transparent material and increase the transmission radiation. In this paper, we first present the metal-insulator phase transition (MIT) of the VO₂ in high and low temperatures. Then we simulate the meta-surface VO₂ of metamaterial reflector by Ansys HFSS to show the emittance tunability (Δε) of the rutile and monoclinic phase of the VO₂. In next section, we will review the recent progress in the deposition of thermochromic VO₂ on glass and silicon substrate with modifying the pressure of sputtering gases and temperature of the substrate. Finally, we present the results of the in-situ sputtered VO_x thin film on thick SiO₂ substrate in different combination of oxygen and argon environment by V₂O₅ target at temperature higher than 300°C and then, analyze it with x-ray diffraction (XRD) method. The thermochromic VO₂ based metamaterial structures open a new route to the passive energy-efficient optical solar reflector in the past few years.