The physics and applications of semiconductor lasers are a very important research area within optoelectronics. Semiconductor lasers were first demonstrated in the 1960s and are very compact high-intensity optical sources, the area of a typical laser chip being about 0.1 mm square. Applications are widespread and include light sources for optical fibre communications, spectroscopy, environmental sensing and biomedical applications.
Many people own a semiconductor laser without even knowing it - inside their CD players.
If the current is low, incoherent light is produced as they recombine spontaneously. The result is optical gain. A laser cavity is formed when some of the light is reflected back into the semiconductor chip by its cleaved facets. PhD student Claire Blay making a semiconductor laser in the clean room. Semiconductor lasers are ideally suited for this type of operation, as they can readily be made so that different sections of the laser cavity can be injected with different current densities, left unbiased, or even reverse-biased.