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,
multi-wavelength lasers from a single material (Update 407),
surface emitting lasers (Update 132,
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