How Does a Laser Diode Work?


Quick Answer

A laser diode works by having a p-n junction that is powered by the injection of electric current. The active medium for these lasers is a semiconductor similar to what is found in light-emitting diodes.

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How Does a Laser Diode Work?
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Full Answer

Laser diodes are formed by doping a thin layer on the surface of a crystal wafer. When the crystal wafer is doped it produces both a p-type region and an n-type region. One region sits above the other, which results in a p-n junction or diode.

A laser diode creates a subset of a larger set of semiconductor p-n junction diodes. When a forward electrical bias is pushed across the laser, two different types of charge carriers — holes and electrons — are injected from different sides of the p-n junction. The holes are injected from the p-doped semiconductor, and the electrons are injected from the n-doped semiconductor.

Because laser diodes are powered by charge injection, they are also commonly called semiconductor lasers. These types of lasers vary greatly from solid state lasers, and they are small and use a low amount of power. Laser diodes can be built into larger arrays, and this is how they become usable for common devices such as CD players and laser printers.

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