Nanobeam Laser Cavities with High Quality-factor and Near-Unity Outcoupling Efficiency

TL;DR

This paper introduces a novel nanobeam cavity design with fins and optimized via perturbation theory, achieving high Q-factors and >90% outcoupling efficiency, validated through fabrication and experimental characterization.

Contribution

It presents a new cavity design with fins, an optimization algorithm for enhancing Q-factor, and experimental validation demonstrating record high quality factors.

Findings

Achieved cavity Q-factors exceeding 170,000 in fabricated passive InP cavities.

Demonstrated unidirectional coupling with >90% extraction efficiency.

Validated the optimization method through experimental results.

Abstract

Cavities with high quality (Q) factor and small mode-volume are crucial to realize high performance nanolasers suitable for optical interconnects. In this work, we propose a novel one-dimensional photonic crystal nanobeam cavity design with fins for controlled electron-injection into the active region. An effective optimization algorithm using first-order perturbation theory of quasinormal modes is implemented and shown to strongly enhance the cavity quality factor. The one-dimensional geometry of the cavity lends itself to unidirectional coupling of the resonant mode into the waveguide by introducing asymmetry of the mirror. The resulting design is shown to achieve high extraction efficiencies ($ >90\% $) while maintaining a high Q-factor ($ > 10 \cdot 10^3$). Through an analysis of the cavity's decay channels, we find that the introduced asymmetry induces unexpected interactions between the cavity's decay channels. Passive InP cavities are fabricated and experimentally characterized, demonstrating record high quality factors exceeding $170 \cdot 10^3$ for designs without fins and up to $70 \cdot 10^3$ for designs with fins, confirming the efficacy of the optimization method and quality of the fabrication process.