Polarization independent grating in a GaN-on-sapphire photonic integrated circuit

Abstract

In this work, we report the realization of a polarization-insensitive grating coupler, single-mode waveguide, and ring resonator in the GaN-on-sapphire platform. We provide a detailed demonstration of the material characterization, device simulation, and experimental results. We achieve a grating coupler efficiency of -5.2 dB/coupler with a 1 dB and 3 dB bandwidth of 40 nm and 80 nm, respectively. We measure a single-mode waveguide loss of -6 dB/cm. The losses measured here are the lowest in a GaN-on-sapphire photonic circuit. This demonstration provides opportunities for the development of on-chip linear and non-linear optical processes using the GaN-on-sapphire platform. To the best of our knowledge, this is the first demonstration of an integrated photonic device using a GaN HEMT stack with 2D electron gas.

Demonstration of ultraviolet III-nitride laser diode with an asymmetric waveguide structure

“…Sapphire is commonly used as a growth substrate for III-Nitride and GaN-based devices, [4] but the significant lattice mismatch between these materials leads to the introduction of significant internal stresses and the formation of numerous crystalline defects. [5] Achieving sufficient optical confinement to facilitate stimulated emission and laser operation presents an additional challenge. While one of the advantages of the III-Nitride materials system is the ability to carefully tune the material bandgap, lattice constant, and index of refraction by alloying GaN with Al or In, it is not possible to alter one parameter without affecting the others.…”