Injection Lasers:

An injection laser, also termed as a laser diode, and is a special form of LED or IRED with a relatively large and flat p-n junction. The injection laser discharges coherent electromagnetic (EM) waves, given the applied current is enough. The Coherent waves are all lined up and all have similar frequency, as compared with the incoherent waves usual of most LEDs and light generating devices in common.

Figure below is a simplified diagram of a laser diode. The substrate is the material in which the component is build; it is such as the foundation of a building. It also serves to take away excess heat therefore the device can carry fairly high current without being damaged. There are mirrors at opposite ends of the piece of n-type material. One of the mirrors (the one labeled in the drawing) is partly reflective. The opposite mirror (not shown) is entirely reflective. The coherent rays appear from the end with the partially reflective mirror.

Figure: Basic cross-sectional drawing of an injection laser, also termed as a laser diode.