Design and fabrication of 980-nm InGaAs/A1GaAs quantum well lasers with low beam divergence

Abstract

We report on the design and fabrication of 980nm InGaAs/AlGaAs double quantum well lasers with low vertical beam divergence. The specially designed structure, which characterized by two low refractive index layers inserted between the cladding and waveguide layers, was theoretically studied using the shooting method and systematic calculation. Results for the beam divergence and far-field distribution are given, and the physical concepts are discussed. Experimental investigation by molecular beam epitaxy was performed. For the fabricated as-cleaved 3micrometers - wide ridge waveguide structure lasers having a cavity length of 800micrometers , a threshold current of 30mA and an external quantum efficiency of 0.8mW/mA were achieved. The measured far field pattern has a vertical divergence of 21 degrees and a horizontal divergence of 8 degrees.