chemical laser

:  a laser that uses a chemical reaction (such as combustion) as an energy source The weapon is the chemical laser, which gets its energy from the combustion of fuels similar to those in rocket engines. Though much of its energy is lost as heat, significant amounts can be extracted by mirrors and resonant chambers, emerging as a concentrated beam of light that in theory can flash across space to zap speeding missiles thousands of miles away. — William J. Broad