Two-Dimensionally Collimated Output Beam from GaAlAs Diode Lasers with Two-Dimensional Distributed Bragg Reflectors

Abstract
A stable and highly collimated output beam (≃1° with 2:1 aspect ratio) was obtained from a two-dimensional distributed Bragg reflector GaAlAs diode laser as a result of a large lasing internal spot (≃50 µmφ), which resulted from a widening in the gratings due to distributed Bragg reflection and the coupling out by the grating coupler. Optimization of the laser structure allowed room temperature operation with low threshold currents. Single longitudinal modes were observed in these two-dimensional oscillations.