Surface-emitting semiconductor lasers and laser arrays

Various types of surface-emitting semiconductor lasers are reviewed along with their anticipated applications. The recent progress in grating-coupled surface-emitting (GSE) lasers is particularly emphasized. SuchGSE arrays have operated continuously to more than 3 W and pulsed to more than 30 W. They have obtainedCW threshold current densities of under 140 A/cm² withCW differential quantum efficiencies of 20 to 40% per surface. Linewidths in the 40 MHz range have been obtained with output powers of 100 to 250 mW. The arrays typically consist of 10–30 mutually injection-coupled gain sections with 10 laterally coupled ridge-guided lasers in each gain section. A single GaInAs strained-layer quantum well with a graded index separate confinement heterostructure geometry allows junction down mounting with light emission through the transparent GaAs substrate. A surface relief grating is used for feedback and outcoupling.