Lateral-Longitudinal Modes of High-Power Inhomogeneous Waveguide Lasers

We present modeling results for lateral-longitudinal modes of longitudinally inhomogeneous finite-length waveguides of ridge semiconductor lasers generating high brightness emission. By numerical solution of the wave equation for a 2-D waveguide, including the output facet, and calculation of the lateral-longitudinal mode threshold (mode lifetime) we show that corrugations of the stripe boundaries along the longitudinal direction cause discrimination of the lateral modes in stripes which are typically wider than those supporting single lateral mode emission. This discrimination is due to higher scattering losses of the higher-order modes in the lateral direction as compared to the fundamental mode. Thus still for wide stripes the output radiation is expected to be single-mode resulting in a high-quality far field with narrow divergence in the lateral direction. Simultaneously, due to the wider stripe width the output emission might have higher power and therefore higher brightness operation can be achieved as compared to a straight stripe without corrugations.