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A laser diode is a semiconductor laser that is closely related to the light emitting diode (LED) both in form and in operation. The laser diode is quite different from the common perception of lasers as big, bulky and power-hungry devices that emit an intense beam of light that can burn or even cut. A laser diode can be considered as an LED that emits focused light and is commonly used in everyday consumer devices such as DVD and Blu-ray players, barcode scanners, fiber optic communication equipment and laser printers.
The laser diode was invented by Dr. Robert Hall of General Electric. He filed his patent on October 24, 1962, and received the patent grant on April 5, 1966, as US Patent no. 3,245,002. The diode emits laser light by bouncing photons back and forth between slices of p-type and n-type semiconductors that are roughly 1 micrometer apart. This is a similar process used in conventional lasers that produce beams by repeatedly pumping the light emitted by the atoms between two mirrors.
The forward biasing done on the semiconductors used in the laser diode forces the two charge carriers (holes and electrons) to be injected or pumped from the opposite side of the p-n junction into the other side called the depletion region, which has zero charge carriers. Because of this, laser diodes are also called injection laser diodes.