| More than three decades have passed since lasing in semiconductors was first observed in several laboratories in 1962 (Hall et al., 1962; Holonyak, Jr. et al., 1962; Nathan et al., 1962; Quist et al., 1962). Although it was one of the first lasers to be demonstrated, the semiconductor laser had to await several important developments, both technological and those related to the understanding of its device physics, before it became fit for applications. Most notably, it was the introduction of heterostructures for achieving charge carrier and photon confinement in the late sixties and the understanding of device degradation mechanisms in the seventies that made possible the fabrication of reliable diode lasers operating with sufficiently low currents at room temperature. In parallel, progress in the technology of low loss optical fibers for optical communication applications has boosted the development of diode lasers for use in such systems. Several unique features of these devices, namely the low power consumption, the possibility of direct output modulation and the compatibility with mass production that they offer, have played a key role in this development. In addition the prospects for integration of diode lasers with other optical and electronic elements in optoelectronic integrated circuits (OEICs) served as a longer term motivation for their advancement.
The next developments that made semiconductor lasers truly ubiquitous took place during the eighties and the early nineties. In the eighties, applications of diode lasers in compact disc players and bar-code readers have benefited from their mass-production capabilities and drastically reduced the prices of their simplest versions. In parallel, more sophisticated devices were developed as the technology matured. Important examples are high power lasers exhibiting very high electrical to optical power conversion efficiency, most notably for solid state laser pumping and medical applications, and high modulation speed, single frequency, distributed feedback lasers for use in long-haul optical communication systems. |
