Schematic of an early Chemical Oxygen-Iodine Laser
Chemlasers are beam weapons which use a chemical reaction to produce a contained field of charged plasma, which is then electrically stimulated between a matched set of mirrors. This causes the charged plasma to lase, producing a powerful pulse of coherent light: a laser beam. Heavy chemlasers are the standard medium-range beam armament on most starships. Smaller chemlasers may be mounted on vehicles, for a light point-defense battery, or even used as heavy weapons by power-armor troopers.
Heavy chemlasers mounted on warships have an effective range of about 800,000 kilometers in the vacuum of space. Smaller chemlasers used on a planetary surface (with an atmosphere) would have a much shorter range.