A laser diode is a small, solid-state equipment that uses semiconductor material to produce continuous light. Materials such as gallium nitride (GaN) or gallium arsenide (GaAs), among others, are used to create them. The laser can be made up of a single diode or a combination of. A laser diode (LD, also injection laser diode or ILD or semiconductor laser or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode's junction. In such a heterostructure of a bipolar interband laser, electrons and holes can recombine, releasing the energy. Laser diode similar to LED is used for producing light but the light is coherent and focused at a small point. It was invented by American physicist Theodore H.