High efficiency, high uniformity, grating coupled surface emitting lasers

GaAs-AlGaAs grating coupled surface emitting lasers are fabricated with superlattice reflectors on the substrate side to increase the output coupling from the second order grating. Differential efficiencies of 60% are achieved with high uniformity over the wafer surface. Spectral uniformity across a 1 cm wafer is better than 0.4 nm while the far field radiation angle from the individual gratings are within 0.02 degrees of the normal. The high uniformity and good lasing characteristics are critical to the coherent coupling of an array of surface emitting devices.