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

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.