The Semiconductor Laser is 40 Years Old

DVDs, barcode scanners, high-speed fiber-optic telecommunications--these multi-billion-dollar technological tokens of the early 21st century all depend upon the semiconductor laser, which was invented 40 years ago in much humbler settings. One of the laser's most prominent children, the CD player, is also celebrating its 20th anniversary this autumn in the consumer market.

In this design, also known as a "diode" laser, electrons and positively charged holes meet at a semiconductor interface to annihilate each other and create light.

Semiconductors can convert electricity into light so efficiently that some physicists scoffed at early reports and complained that this design, very different from the original solid-state and gas lasers, required breaking the second law of thermodynamics in order to work as advertised.

But starting in September 1962, scientists reported functioning diode lasers from four independent laboratories--GE (at two different research centers), IBM, and MIT's Lincoln Lab, where the corporate ethos of the day allowed physicists to pursue research on esoteric topics even without likely applications or a guarantee of success.

The four groups' results appeared within three months of each other in the journals Physical Review Letters and Applied Physics Letters, the latter journal then in its first year of publication.

Technological development of the semiconductor laser continues to this day. Examples include quantum cascade lasers (see Updates 181, 322, 359), multi-wavelength lasers from a single material (Update 407), surface emitting lasers (Update 132, 217, 229) and blue lasers (Update 50). Within the decade, blue lasers might replace red lasers in DVD players, enabling a six-fold increase in information on the same-sized disk.

Hand in hand with diode lasers is the visible LED, also invented in 1962. The low-power, high efficiency LEDs have found their way into traffic signals and automobile and bus tail lights. Recently available white-light LEDs have become powerful enough to replace incandescent front headlights in some automobile models, a development that even some of the most optimistic LED designers would have found ludicrous a quarter of a century ago. (Also see AIP/OSA news release.)