A diode laser passes an electric current through a semiconductor material, typically gallium arsenide, causing electrons and holes to recombine and emit photons through spontaneous emission. The photons then trigger additional electrons to emit more photons in stimulated emission. Telecommunication, barcode readers, and medical equipment use diode lasers for their small size, efficiency, and continuous or pulsed. Also called laser diode welding, semiconductor (LD) laser welding is a technique that uses a laser beam generated by an electric current passing through a semiconductor as the heat source. It belongs to the class of semiconductor lasers and is structurally similar to a light-emitting diode (LED), but differs in its ability to provide optical. The laser diode chip is the small black chip at the front; a photodiode at the back is used to control output power. SEM (scanning electron microscope) image of a commercial laser diode with its case and window cut away.
