Surface-emitting, single-lobe operation from 2nd-order DFB/DBR lasers with central grating phaseshift

Here we present a composite DFB/DBR device, which fundamentally favors lasing in the symmetric mode over a wide range in central-phaseshift value. External differential quantum efficiencies in excess of 50% are obtained, and the guided-field profile is substantially uniform. A double-quantum-well InGaAs-InGaAsP active region with InGaP cladding layers, and a grating formed in the p+-GaAs cap layer. A GaAs-Au grating provides both high coupling coefficient, K, as well as insures that all first-order diffracted light is collected.