A laser diode is a small device that is similar in construction and appearance to a light emitting diode (LED). The main difference is that a laser diode produces coherent laser light while an LED produces incoherent light. Ever since they were first invented in 1962, millions of laser diodes have been used in a wide range of consumer and industrial products.

History

The first laser diode was invented by a team of researchers at General Electric in 1962 but many other research teams also contributed to their initial development. The common heterojunction laser diode was created from the combined research of Herbert Kroemer and Zhores Alferov, who were both awarded the Nobel Prize in 2000.

How Laser Diodes Work

Laser diodes are manufactured using the same processes used to make other semiconductors, like computer chips and solar cells. The main difference is that laser diodes have a long and narrow channel between the semiconductor layers that acts as a waveguide for the laser light. As with other light emitting diodes, when an electrical current flows through through a laser diode, charge carriers combine where the semiconductor layers meet and energy is released as light. The light is confined inside the waveguide where it is reflected and amplified until it exits through one end.

Types

There are many difference types of laser diode, each with a different arrangement of semiconductor layers. The basic type which uses two semiconductor layers is very inefficient. Better designs have multiple layers which increase the laser power by combining more charge carriers and trapping more light inside the waveguide. The most common types of laser diode are the heterostructure, quantum well, and distributed feedback.

While laser diodes are sometimes called semiconductor lasers, they are not usually called solid-state lasers. In electronics, solid-state and semiconductor generally mean the same thing. However, lasers are defined by the type of material used to produce their light, and solid-state lasers use materials like ruby. While the power of a single laser diode is low, many can be grouped together to form a single high-power laser.

Applications

Laser diodes are most commonly used in optical media players to read data from CDs, DVDs, HD-DVDs, and Blu-ray discs. They are used to produce the light pulses that travels through optical fibers to link computer networks together. Laser printers use laser diodes to create the static charges that attract toner particles to their print drums. Handheld laser pointers used for presentations use laser diodes, and they are used in devices that measure distances and check levels. More powerful laser diodes are used in surgery to precisely burn tissue, and in manufacturing to cut and etch materials.