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Published online by Cambridge University Press: 31 January 2011
Robert N. Hall, born in New Haven, Connecticut in 1919, joined General Electric's Research and Development Center after graduating from the California Institute of Technology. In 1962, having realized that a semiconductor junction could support population inversion, Hall built the first semiconductor injection laser. This device, based on a specially designed p-n junction, operated when an electric current injected the electrons directly into the junction, thus allowing for highly efficient generation of coherent light from a compact source. Today, diode lasers based on Hall's original idea are used, among other places, in CD and DVD players, laser printers, and fiber-optic communication systems.
In this chapter we describe the basic features of the beam of light emitted by a diode laser, and discuss methods to analyze and manipulate this beam. Collimation and beam-shaping with a pair of cylindrical lenses will be shown to be a simple and flexible method that may be applied not only to diode lasers but also to beams emerging from optical fibers.
Characteristics of diode lasers
A semiconductor diode laser shown schematically in Figure 34.1 consists of a gain layer (only a few ten nanometers thick), surrounded by guiding layers for confining the laser mode. The guiding layers' index of refraction is somewhat greater than that of the surrounding regions (substrate and cladding), thus permitting confinement by total internal reflection.
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