Searcharxiv⌕ Search

arXiv subjects

Geza Kurczveil

Publications and source records attributed to Geza Kurczveil.

11 recordsLinked to original sources
arXiv2026

Single-Mode Control of High-Speed and Low-Threshold III-V/Si Quantum Dot Microring Lasers via Azimuthal Gratings

Hybrid III-V/silicon quantum-dot microring lasers are compact, energy-efficient O-band sources, but their whispering-gallery cavities are inherently multimode and bidirectional, producing unstable mode hopping that is incompatible with dense wavelength-division multiplexing. We show that an azimuthal grating patterned into the silicon ring - a single lithographic degree of freedom - converts this multimode cavity into a wavelength-addressed, single-mode source. A coupled-mode analysis derives the angular-momentum selection rule from first principles and shows that the inner-wall corrugation replaces the degenerate counter-propagating pair with symmetric and anti-symmetric standing-wave supermodes of unequal radiative loss. At the second-order Bragg condition the anti-symmetric mode is symmetry-protected, yielding a high-quality-factor state at exactly one azimuthal order; finite-element simulations confirm this and identify grating depth as the primary loss-engineering handle. Devices fabricated in-house on a 100 mm silicon-on-insulator platform hold a single longitudinal order with a side-mode suppression ratio of 37.9 dB and continuous, hop-free tuning, while the emission wavelength stays fixed across a factor-of-two change in cavity loading, set lithographically rather than by the gain peak. Because the grating decouples the lasing wavelength from the quantum-dot gain, the detuning becomes a mask-level design variable that sets the temperature of minimum threshold current, reaching 1.95 mA near 50 °C. Combined with side-mode suppression beyond 37 dB and multi-gigahertz direct modulation, these lasers are practical building blocks for cascaded, wavelength-addressed transmitter arrays in data communication and co-packaged optics.

physics.optics↗
arXiv2026

Demonstration and Design of Uni-Directional and Ultra-Low Threshold Hybrid Quantum Dot III-V/Si Micro-Ring Laser

Micro-ring lasers (MRLs) are attractive light sources for energy-efficient optical interconnects, but their intrinsic directional bistability leads to unpredictable clockwise/counter-clockwise emission. We demonstrate stable unidirectional emission in hybrid quantum-dot (QD) III-V/Si MRLs using passive reflective feedback integrated on the bus waveguide, leaving the ring cavity unperturbed. Three reflector architectures - Y-splitter loop mirrors, adiabatic Y-splitter loop mirrors, and distributed Bragg reflectors (DBRs) - are benchmarked against a reflector-free bidirectional baseline through combined experiment and coupled-mode-theory rate-equation modeling. All designs preserve ultra-low thresholds of 0.79-1.12 mA (112-158 A/cm^2, roughly an order of magnitude below prior quantum-well unidirectional ring lasers) while enhancing single-facet output power and wall-plug efficiency, with directional isolation up to 27.65 dB for the DBR. The reflectors impose no penalty on the 4-5 GHz modulation bandwidth or its thermal robustness, establishing passive external feedback as a practical route to unidirectional QD MRLs for DWDM-scale optical interconnects.

physics.optics↗
arXiv2026

Experimental Design Space Exploration of Ultra-Low Threshold Hybrid III-V/Si Quantum Dot Microring Lasers

In this work, we report on the design strategies and experimental validation of ultra-low threshold ($< 0.8\,\mathrm{mA}$) hybrid III--V/Si quantum dot (InAs/GaAs) micro-ring lasers with optical output powers $> 2\,\mathrm{mW}$ for $1.3\,μ\mathrm{m}$ emission. The multi-dimensional design exploration allows for the demonstration of record wall-plug efficiencies ($\sim 10\%$) and threshold current densities ($109\,\mathrm{A/cm^2}$) for these compact sources on silicon. We also demonstrate the thermal performance of several designs with record characteristic temperature values of $T_0 = 212\,\mathrm{K}$, indicating minimal temperature dependence of the threshold current. In addition, the high differential gain allows for the demonstration of 3-dB bandwidths up to $5\,\mathrm{GHz}$.

physics.optics↗
arXiv2026

A Non-Volatile Heterogeneous Quantum Dot III-V/Si DFB Laser with Optical Memristive Behavior

In this work, we introduce a non-volatile heterogeneous quantum dot (QD) III-V/Al2O3/Si distributed feedback (DFB) laser exhibiting optical memristive behavior. The device operates in the O-band (~1300 nm) with a threshold current density of 234 A/cm2 and a side-mode suppression ratio exceeding 48 dB. Co-integrated Al2O3-based memristors produce bipolar resistive switching, yielding non-volatile wavelength shifts of ~ 46 pm and ~ 17 dB peak power contrast with zero static holding power. The III-V/Al2O3/Si heterojunction memristor I-V hysteresis is also modeled. This new device enables simultaneous coherent light generation and persistent optical state storage, establishing a new class of active photonic memory for neuromorphic and reconfigurable WDM applications.

physics.optics↗
arXiv2026

Scalable Back-Propagation-Free Training of Optical Physics-Informed Neural Networks

Physics intelligence and digital twins often require rapid and repeated performance evaluation of various engineering systems (e.g. robots, autonomous vehicles, semiconductor chips) to enable (almost) real-time actions or decision making. This has motivated the development of accelerated partial differential equation (PDE) solvers, in resource-constrained scenarios if the PDE solvers are to be deployed on the edge. Physics-informed neural networks (PINNs) have shown promise in solving high-dimensional PDEs, but the training time on state-of-the-art digital hardware (e.g., GPUs) is still orders-of-magnitude longer than the latency required for enabling real-time decision making. Photonic computing offers a potential solution to address this huge latency gap because of its ultra-high operation speed. However, the lack of photonic memory and the large device sizes prevent training real-size PINNs on photonic chips. This paper proposes a completely back-propagation-free (BP-free) and highly salable framework for training real-size PINNs on silicon photonic platforms. Our approach involves three key innovations: (1) a sparse-grid Stein derivative estimator to avoid the BP in the loss evaluation of a PINN, (2) a dimension-reduced zeroth-order optimization via tensor-train decomposition to achieve better scalability and convergence in BP-free training, and (3) a scalable on-chip photonic PINN training accelerator design using photonic tensor cores. We validate our numerical methods on both low- and high-dimensional PDE benchmarks. Through pre-silicon simulation based on real device parameters, we further demonstrate the significant performance benefit (e.g., real-time training, huge chip area reduction) of our photonic accelerator.

cs.LG↗
arXiv2024

Real-Time FJ/MAC PDE Solvers via Tensorized, Back-Propagation-Free Optical PINN Training

Solving partial differential equations (PDEs) numerically often requires huge computing time, energy cost, and hardware resources in practical applications. This has limited their applications in many scenarios (e.g., autonomous systems, supersonic flows) that have a limited energy budget and require near real-time response. Leveraging optical computing, this paper develops an on-chip training framework for physics-informed neural networks (PINNs), aiming to solve high-dimensional PDEs with fJ/MAC photonic power consumption and ultra-low latency. Despite the ultra-high speed of optical neural networks, training a PINN on an optical chip is hard due to (1) the large size of photonic devices, and (2) the lack of scalable optical memory devices to store the intermediate results of back-propagation (BP). To enable realistic optical PINN training, this paper presents a scalable method to avoid the BP process. We also employ a tensor-compressed approach to improve the convergence and scalability of our optical PINN training. This training framework is designed with tensorized optical neural networks (TONN) for scalable inference acceleration and MZI phase-domain tuning for \textit{in-situ} optimization. Our simulation results of a 20-dim HJB PDE show that our photonic accelerator can reduce the number of MZIs by a factor of $1.17\times 10^3$, with only $1.36$ J and $1.15$ s to solve this equation. This is the first real-size optical PINN training framework that can be applied to solve high-dimensional PDEs.

cs.LG↗
arXiv2023

Energy-Efficient Photonic Memory Based on Electrically Programmable Embedded III-V/Si Memristors: Switches and Filters

We demonstrate non-volatile optical functionality by embedding multi-layer $HfO_2/Al_2O_3$ memristors with III-V/Si photonics. The wafer-bonded III-V/Si memristor facilitates non-volatile optical functionality for a variety of devices such as Mach-Zehnder Interferometers (MZIs), and (de-)interleaver filters. The MZI optical memristor exhibits non-volatile optical phase shifts $> π(Δn_{g} > 2.70 \times 10^{-3}$) with ~ 30 dB extinction ratio while consuming 0 electrical power consumption in a true "set-and-forget" operation. We demonstrate 6 non-volatile states with each state capable of 4 Gbps modulation. III-V/Si (de-)interleavers were also demonstrated to exhibit memristive non-volatile passband transformation with full set/reset states. Time duration tests were performed on all devices and indicated non-volatility up to 24 hours and most likely beyond. To the best of our knowledge, we have demonstrated for the first time, non-volatile III-V/Si optical memristors with the largest electric-field driven phase shifts and reconfigurable filters with the lowest power consumption.

physics.optics↗
arXiv2023

Non-volatile heterogeneous III-V/Si photonics via optical charge-trap memory

We demonstrate, for the first time, non-volatile charge-trap flash memory (CTM) co-located with heterogeneous III-V/Si photonics. The wafer-bonded III-V/Si CTM cell facilitates non-volatile optical functionality for a variety of devices such as Mach-Zehnder Interferometers (MZIs), asymmetric MZI lattice filters, and ring resonator filters. The MZI CTM exhibits full write/erase operation (100 cycles with 500 states) with wavelength shifts of $Δλ_{non-volatile} = 1.16 nm$ ($Δn_{eff,non-volatile} ~ 2.5 \times 10^{-4}$) and a dynamic power consumption $<$ 20 pW (limited by measurement). Multi-bit write operation (2 bits) is also demonstrated and verified over a time duration of 24 hours and most likely beyond. The cascaded 2nd order ring resonator CTM filter exhibited an improved ER of ~ 7.11 dB compared to the MZI and wavelength shifts of $Δλ_{non-volatile} = 0.041 nm$ ($Δn_{eff, non-volatile} = 1.5 \times 10^{-4}$) with similar pW-level dynamic power consumption as the MZI CTM. The ability to co-locate photonic computing elements and non-volatile memory provides an attractive path towards eliminating the von-Neumann bottleneck.

physics.optics↗
arXiv2023

Fast and energy-efficient non-volatile III-V-on-silicon photonic phase shifter based on memristors

Silicon photonics has evolved from lab research to commercial products in the past decade as it plays an increasingly crucial role in data communication for next-generation data centers and high performance computing1. Recently, programmable silicon photonics has also found new applications in quantum2 and classical 3 information processing. A key component of programmable silicon photonic integrated circuits (PICs) is the phase shifter, traditionally realized via the thermo-optic or plasma dispersion effect which are weak, volatile, and power hungry. A non-volatile phase shifter can circumvent these limitations by requiring zero power to maintain the switched phases. Previously non-volatile phase modulation was achieved via phase-change4 or ferroelectric materials5, but the switching energy remains high (pico to nano joules) and the speed is slow (micro to milli seconds). Here, we report a non-volatile III-V-on-silicon photonic phase shifter based on HfO2 memristor with sub-pJ switching energy (~400fJ), representing over an order of magnitude improvement in energy efficiency compared to the state of the art. The non-volatile phase shifter can be switched reversibly using a single 100ns pulse and exhibits an excellent endurance over 800 cycles. This technology can enable future energy-efficient programmable PICs for data centers, optical neural networks, and quantum information processing.

physics.optics↗
arXiv2023

Tensorized Optical Multimodal Fusion Network

We propose the first tensorized optical multimodal fusion network architecture with a self-attention mechanism and low-rank tensor fusion. Simulation results show $51.3 \times$ less hardware requirement and $3.7\times 10^{13}$ MAC/J energy efficiency.

eess.SP↗