Laser diode structures typically employ
A laser diode consists of the p-n junction where both electrons and holes are involved. An excess of negatively charged carriers, or electrons, is produced by the n-type area, and an excess of positively charged carriers, or holes, is produced by the p-type. These devices are capable of producing an intense laser ray with uniformly sized light waves. The laser diode principle involves three fundamental processes: absorption, spontaneous emission, and stimulated emission. For laser action, stimulated emission must dominate, requiring population inversion achieved through electrical pumping. The basic device structure consists of a rectangular parallelepiped of a direct bandgap semiconductor, usually a III–V compound semiconductor such as GaAs, incorporat-ing a forward-biased, heavily doped p–n junction to provide the optical gain medium in a resonant optical cavity, as illustrated.
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