Laserdiode

A laser diode is a semiconductor device that emits coherent light through stimulated emission when electrical current is injected into a p-n junction. Unlike ordinary LEDs, laser diodes incorporate an optical cavity formed by the end facets or by mirrors in a polished structure, providing feedback that narrows the emission into a beam with a small linewidth.

Most commercial laser diodes use quantum-well active regions and are produced from gallium arsenide (GaAs) or indium phosphide (InP) materials for infrared wavelengths, while gallium nitride (GaN) enables blue and green output. Edge-emitting diodes produce beams along the plane of the chip, whereas vertical-cavity surface-emitting lasers (VCSELs) emit from the top surface with efficient coupling to multimode fibers.

Key parameters include threshold current, slope efficiency, wavelength, output power, and heat management. They are widely used in telecommunications, data storage and transfer, barcode scanning, laser printers, medical instruments, and sensing equipment.

Performance is temperature dependent; changes in temperature shift the emission wavelength and raise the threshold current. Devices require heat sinking or thermoelectric cooling to maintain stable operation and long lifetime.

The first electrically pumped laser diode was demonstrated in 1962, and subsequent advances in semiconductor heterostructures and epitaxial growth led to high-efficiency devices such as VCSELs and high-power edge emitters.