Measurement and simulation of the lateral mode profile of broad ridge 405 nm (Al,In)GaN laser diodes

Abstract

For broad ridge (Al,In)GaN laser diodes, which are inevitable for high output power applications in the UV and blue spectral range, filaments or higher order lateral modes build p, which influence the far-field beam quality. We investigate the lateral profile of the optical laser mode in the waveguide experimentally by temporal and spectral resolved scanning near-field optical microscopy measurements on electrically pulsed driven laser diodes and compare these results with one-dimensional simulations of the lateral laser mode in the waveguide. We present a model that describes the optical mode profile as a superposition of different lateral modes in a refractive index profile which is modified by carrier- and thermal-induced effects. In this way the mode dynamics on a nanosecond to microsecond time scale can be explained by thermal effects.