arXiv subjects

Claire Gmachl

Publications and source records attributed to Claire Gmachl.

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↗

arXiv2021

Correction to the Effective Refractive Index and the Confinement Factor in Waveguide Modeling for Quantum Cascade Lasers

The equations for the effective medium refractive index and for the confinement factor in the waveguide design for quantum cascade lasers are derived.Compared to equations used in prior literature, by applying rigorous perturbation theory and including the effect of the anisotropic optical gain and non-Hermitian properties of the waveguide structure and materials, a few percent correction should be made to the confinement factor and the effective gain. This result can easily be generalized to any optical devices with a layered structure.

physics.optics↗

arXiv2005

Compact Quasi-Chaotic Optical Cavity

A novel, 3-dimensional, convex, multi-pass optical cavity with partially-chaotic ray dynamics is presented. The light is localized near stable, long-path length trajectories supported by the cavity, and beam diffraction is suppressed by the phase space barriers between the regions of regular and chaotic ray dynamics that are generally present in partially-chaotic systems. For a centimeter-size cavity, the design supports meter-scale optical path lengths, suggesting future applications in trace gas detection. An exemplary cavity has been fabricated from a hollow, gold-coated, acrylic shell. Our measurements using a HeNe laser and a pulsed red diode laser for characterization of the cavity beam pattern and optical path length, respectively, confirm the theoretically predicted optical dynamics and the ability of the cavity to support meter-scale path lengths.

physics.optics↗

arXiv2003

Experimental demonstration of a high quality factor photonic crystal microcavity

Sub-threshold measurements of a photonic crystal (PC) microcavity laser operating at 1.3 microns show a linewidth of 0.10 nm, corresponding to a quality factor Q ~ 1.3x10^4. The PC microcavity mode is a donor-type mode in a graded square lattice of air holes, with a theoretical Q ~ 10^5 and mode volume Veff ~ 0.25 cubic half-wavelengths in air. Devices are fabricated in an InAsP/InGaAsP multi-quantum well membrane and are optically pumped at 830 nm. External peak pump power laser thresholds as low as 100 microWatts are also observed.

quant-ph↗

arXiv1998

High-Power Directional Emission from Microlasers with Chaotic Resonators

High-power and highly directional semiconductor cylinder-lasers based on an optical resonator with deformed cross section are reported. In the favorable directions of the far-field, a power increase of up to three orders of magnitude over the conventional circularly symmetric lasers was obtained. A "bow-tie"-shaped resonance is responsible for the improved performance of the lasers in the higher range of deformations, in contrast to "whispering-gallery"-type modes of circular and weakly deformed lasers. This resonator design, although demonstrated here in midinfrared quantum-cascade lasers, should be applicable to any laser based on semiconductors or other high-refractive index materials.

cond-mat.mes-hall↗