A source of light which produce
light radiations by stimulated emission when it is placed between two mirrors
(optical cavity) is known as semiconductor injection laser. Here photons are
produced by stimulated emission which is due to the recombination of injected
carriers. On proper amplification, semiconductor injection laser gives high
radiance in terms of mill watts of laser power.
Line width of laser is very narrow and hence semiconductor injection
laser is highly monochromatic. Line width is always less than 10 Å. Provision
for increasing modulation bandwidth, high degree of temporal coherence,
moderate spatial coherence and high focusing power are the other characteristics
of this type of laser. A modified version of injection laser, called stripe
geometry double heterostructure laser provides high degree of carrier and
optical confinement in active region. In a gain guided injection laser, optical
mode distribution along the junction plane is determined from optical gain.
