A laser diode is a laser where the active medium is a semiconductor similar to that found in a light emitting diode. Laser diode is formed by doping a very thin layer on the surface of a crystal water. They find wide use in optical communication as easily coupled light sources. Diode lasers are efficient sources of high power radiation and with suitable beam shaping technology the output can be easily launched into the cladding of a suitably designed fibre. Hence, preferred in optical communication. They also consume less power.