Semiconductor lasers take the strain

Abstract

Compact infrared lasers made from gallium arsenide and indium phosphide have opened up many significant opportunities over the past decade – optical communications, compact discs and related optical data storage applications, in particular. The recent commercialisation of visible semiconductor lasers by Toshiba and others opens up potentially huge markets in displays and lighting. Until now most of these lasers have been based on lattice-matched structures with the materials in each layer of the semiconductor structure having the same lattice constant. But there are only a few suitable combinations of lattice-matched materials for laser applications and these cover only very limited wavelength ranges. They also suffer from serious intrinsic loss mechanisms. Therefore a lot of effort is currently being directed towards increasing the range of available wavelengths and reducing these losses, and “strained-layer” lasers are proving most successful in this quest.