arXiv subjects

Sara Kacmoli

Publications and source records attributed to Sara Kacmoli.

5 recordsLinked to original sources

arXiv2025

Amplified Feedback and Spontaneous Emission Injection in Quantum Cascade Ring Laser Systems

Ring lasers exhibit rich operational regimes such as unidirectional, bidirectional, or bistable operation. The two-mode dynamics of the counter-propagating modes - clockwise (CW) and counterclockwise (CCW) and their selection, have gained attention in the mid-infrared; however, the underlying switching mechanism has been largely unexplored. Previously, we experimentally demonstrated robust and deterministic mode selection in a ring quantum cascade laser (QCL) with an active outcoupling waveguide. Here, we apply the Lang-Kobayashi framework to our system to model the effects of spontaneous emission in the waveguide arms as well as amplified optical feedback from the facets on the mechanics of mode switching. We find that coherent feedback from facet reflections agrees upwards of 93\% with the experimental behavior, indicating that amplified feedback is the dominant mechanism driving the mode selection dynamics.

physics.optics↗

arXiv2024

Hole-Based Stealthy Hyperuniform Semiconductor Metamaterials for the Mid-Infrared

Stealthy hyperuniform heterostructures are a novel type of metamaterial with the potential for optical image processing at angles away from normal incidence. These metamaterials show analogous properties to photonic crystals while circumventing the spatial anisotropy often hindering the latter's use. In this paper, we have successfully designed, fabricated, and characterized a hole-based stealthy hyperuniform structure on a quantum cascade layer substrate. The infrared spectral data reveal a sizable gap-midgap ratio of 9.8% for a photonic band gap around $12.0 ~μm$ in the form of an enhanced reflection region for increasing incidence angles. The stealthy hyperuniform metamaterial also showed spatial isotropy by its unchanging reflection spectrum for all in-plane rotational angle measurements.

physics.optics↗

arXiv2023

Efficient computation of coherent multimode instabilities in lasers using a spectral approach

Coherent multimode instabilities are responsible for several phenomena of recent interest in semiconductor lasers, such as the generation of frequency combs and ultrashort pulses. These techonologies have proven disruptive in optical telecommunications and spectroscopy applications. While the standard Maxwell-Bloch equations encompass such complex lasing phenomena, their integration is computationally expensive and offers limited analytical insight. In this paper, we demonstrate an efficient spectral approach to the simulation of multimode instabilities via a quantitative analysis of the instability of single-frequency lasing in ring lasers, referred to as the Lorenz-Haken (LH) instability or the Risken-Nummedal-Graham-Haken (RNGH) instability in distinct parameter regimes. Our approach, referred to as CFTD, uses generally non-Hermitian Constant Flux modes to obtain projected Time Domain equations. CFTD provides excellent agreement with finite-difference integration of the Maxwell-Bloch equations across a wide range of parameters in regimes of non-stationary inversion, including frequency comb formation and spatiotemporal chaos. We also develop a modal linear stability analysis using CFTD to efficiently predict multimode instabilities in lasers. The combination of numerical accuracy, speedup, and semi-analytic insight across a variety of dynamical regimes make the CFTD approach ideal to analyze multimode instabilities in lasers, especially in more complex geometries or coupled laser arrays.

physics.optics↗

arXiv2023

Photonic molecule based on coupled ring quantum cascade lasers

Photonic molecules - particular systems composed of coupled optical resonators - emulate the behavior of complex physical systems exhibiting discrete energy levels. In this work, we present a novel photonic molecule composed of two strongly coupled, mid-infrared ring quantum cascade lasers. We explore both experimentally and numerically the key features of the photonic molecule such as the energy level splitting of bonding and antibonding supermodes. Due to the large size of the resonators, the energy splitting results in bands containing tens of modes. Each of these modes is furthermore doubly degenerate with respect to the direction of propagation, namely clockwise and counterclockwise. We explore several methods to carefully break these symmetries of the system in a controlled manner by introducing spatial and temporal asymmetries in the pumping scheme of the ring lasers. By employing these techniques, we achieve a high degree of precision in the dynamic control of the photonic molecule. Owing to their inherent suitability for on-chip integration, this new class of devices may enable applications as varied as novel mid-infrared sensors or a rich playground for studying non-Hermitian photonics and quantum optics with quantum cascade lasers.

physics.optics↗

arXiv2022

Unidirectional mode selection in bistable quantum cascade ring lasers

Ideal ring resonators are characterized by travelling-wave counterpropagating modes, but in practice travelling waves can only be realized under unidirectional operation, which has proved elusive. Here, we have designed and fabricated a monolithic quantum cascade ring laser coupled to an active waveguide that allows for robust, deterministic and controllable unidirectional operation. Spontaneous emission injection through the active waveguide enables dynamical switching between the clockwise and counterclockwise states of the ring laser with as little as 1.6% modulation of the electrical input. We show that this behavior stems from a perturbation in the bistable dynamics of the ring laser. In addition to switching and bistability, our novel coupler design for quantum cascade ring lasers offers an efficient mechanism for outcoupling and light detection.

physics.optics↗