Laser - How It Works

The laser consists of the following components: the pump, which is the source of energy to drive the laser; the active medium, which is where the stored energy is converted into the laser light through the process of stimulated emission; the optical cavity, which is usually made up of a pair of mirrors, one whose reflectivity at the wavelength of the laser is as close to 100% as possible and the other with a reflectivity less than 100%, through which the output beam propagates.