Continuous‐Wave Operation of 457 nm InGaN Laser Diodes with Etched Facet Mirrors for On‐Chip Photonics

Abstract

The success of silicon photonics is sparking widespread interest in photonic integrated circuits at visible light wavelengths using SiN and other waveguiding platforms. Compact active circuits desire the heterogeneous integration of GaN‐based laser diodes. Herein, the optimization of smooth and vertical facets is reported using a combination of inductively coupled plasma etching followed by wet etching with a tetramethylammonium hydroxide‐based solution. Facet quality for concave‐, flat‐, and convex‐shaped structures surrounding the mirror is compared. Convex‐shaped structures result in the highest facet quality due to the evolution of the crystal plane‐dependent etching. 2 μm‐wide ridge waveguide, etched facet Fabry–Pérot cavity lasers with length of 1.5 mm emitting at 457 nm are realized using the optimized process. The lasers deliver up to 28 mW of optical power at 250 mA under continuous wave with slope efficiency of 0.26 W A−1 and lasing threshold current density of 4.6 kA cm−2.