Gallium Nitride-Based Moiré Photonic Crystals for Applications in Microcavity Lasing

Abstract

Gallium Nitride (GaN) microcavity lasers are powerful devices with applications in lighting, optical communication, and sensing. In conventional microcavities, GaN-based emitters in the visible wavelength range have been shown to exhibit ultralow thresholds lasing despite containing significant levels of growth-related defects. In unconventional microcavities, GaN’s highly efficient light emission presents an opportunity to demonstrate novel light localization mechanisms that can be utilized in lasing. Moiré photonic crystals are unconventional microcavities that slow and localize light propagation via coupling between two stacked, twisted photonic crystal layers. The two layers in the stack provide design degrees of freedom that can enable active tunability of the cavity. This work probes the feasibility of moiré photonic crystal lasers with GaN-based emitting materials. Lasing is demonstrated in a single layer, merged moiré photonic crystal at wavelengths of 450 and 451nm with a threshold of 30μJ/cm2. A fabrication protocol is developed to realize true bilayer GaN photonic crystal systems, paving a way for active tunability. Finally, to be realized in a compact piece of technology, GaN-based microcavities must be able to be controlled electrically. The last chapter of this work explores electrical control of microdisk cavities in GaN, developing a fabrication protocol and identifying key design challenges in electrical injection.