OVERVIEW

From its inception in 1962, the semiconductor laser based on GaAs and related III–V compounds has evolved into an extraordinary and versatile optoelectronic device. Today we find this ubiquitous, relatively low-cost, high-efficiency coherent light source used in a wide spectrum of applications ranging from long-haul optical communications systems to high-density optical data storage. The evolution of these devices to their present state of sophistication – with wall-plug efficiencies of 50% and greater in the conversion of DC electric current to coherent photons (as one illustrative characteristic) – did not happen overnight, however. Nearly two decades of research and development were spent before the edge-emitting GaAs-based diode laser emerged as a mature optoelectronic technology suited for applications and integration. Once the basic guiding scientific principles were established in the design of these devices, making specific use of optical and electronic confinement in heterostructures, a major challenge remained at the basic materials science level. This challenge concerned the role of crystal defects, both point and extended-state in nature, which were found to lead to degradation and early burnout of the lasers. However, advances in epitaxial techniques, in the III–V arsenide and phosphide systems, together with improvements in the device fabrication techniques, led to the development of low threshold current density quantum well (QW) heterostructure lasers, which are now contributing to the revolution in optical network technology.

The history of semiconductor light emitters at the short visible wavelengths stands in sharp contrast.