Semiconductor Laser

Semiconductor Laser. 

A solid-state laser is a laser that uses a gain medium that is a solid, rather than a liquid as in dye lasers or a gas as in gas lasers. Semiconductor-based lasers are also in the solid state, but are generally considered as a separate class from solid-state lasers, called laser diodes.

The physics of the quantization, in the case of semiconductor lasers, is very different. In addition, solid-state lasers are always optically pumped, whereas semiconductor lasers are excited by the passage of electric current through them.

semiconductor laser is basically a p-i-n diode. When it is forward-biased, electrons in the conduction band and holes in the valence band are injected into the intrinsic region from the n-type doped and the p-type doped regions, respectively.

Common Semiconductor Materials
Common materials for semiconductor lasers (and for other optoelectronic devices), all having a direct band gap, are

GaAs (gallium arsenide)
AlGaAs (aluminum gallium arsenide)
GaP (gallium phosphide)
InGaP (indium gallium phosphide)
GaN (gallium nitride)
InGaAs (indium gallium arsenide)
GaInNAs (indium gallium arsenide nitride)
InP (indium phosphide)
GaInP (gallium indium phosphide)