Ion lasers (also known as gas-ion lasers) emit high-powered beams in the visible and ultraviolet (UV) spectral ranges. Ion lasers are composed of a plasma tube, a vacuum- sealed alumina (or ceramic envelope), and a number of windows or mirrors. The plasma tube is filled with ionized gases that settle into levels with transitions between. When these ionized gases are electrically stimulated, radiation is emitted into the alumina. The ends of the alumina are either two Brewster windows, or one Brewster window and a sealed cavity mirror. The area between is referred to as the optical cavity. A 100-percent-reflecting mirror and a partially transmissive output-coupling mirror define the optical cavity. From here, the emitted radiation is focused into a high-powered, high quality beam with a moderate to high continuous-wave output of typically 1 mW to 10 W. In single-frequency operation, the high reflector is replaced with a Brewster prism, and an etalon is inserted.

