Gas lasers, chemical lasers and solid state lasers were generally used in medicine or industry, but had little use in warfare. Early laser weapons were inefficient, converting as little as 10% of the input energy into the output light beam. As technology advanced, so did laser efficiency, until laser weapons approached or exceeded 90% efficiency.
Early weapons were heat rays that cause damage primarily through thermal mechanisms. The energy of the beam directly heats the target, causing charring, melting, ignition, and vaporization. A continuous-wave High Energy Laser (HEL) beam is a focused ray of optical radiation, which simply delivers heat to the surface of a target.
Then came blasters which cause mechanical damage by emitting ultra-short pulses of extreme intensity, causing matter to flash suddenly into plasma. The resulting explosion creates a shockwave which causes damage comparable to a heat ray with one tenth to one hundredth the amount of input energy.
Lasers adopt a wide range of wavelengths from the electromagnetic spectrum. Visible and near visible wavelengths have the best performance in an atmosphere and x-ray wavelengths are ideal for space combat, due to their extremely short wavelengths that allow them to be focused at long distances.
| Free Electron Lasers | These can be tuned to produce laser beams of a very wide range of frequencies, up to and including x-rays. A beam of electrons is shot through an wiggly magnetic field to produce an intense beam of coherent light. A typical free electron x-ray laser gunship may attack targets many astronomical units away. Visible and near visible free electron lasers must be mounted in fixed installations or very large vehicles such as sea ships, jet aircraft, or orbital bombardment spacecraft. |
| Diode Lasers | These can be small and hand-held. They use a diode to stimulate light emission from a semiconducting substrate and use manufactured optical resonators to generate a beam. By phase locking the beam by means of a phase-conjugate "mirror", very high efficiency beams can be generated. More advanced systems use quantum wells or quantum dots. Lasers of this type often operate in the near infrared or visible part of the spectrum. The most advanced forms can be more than 90% efficient at converting energy input into light. |
| Optical Phased Arrays | An Optical Phased Array consists of layers of light emitting material, sensors and associated processors. Such an array can be used as an interplanetary or even interstellar weapon. Entire warships, habitats or even planet-sized objects are used as phased array lasers. Using a visible wavelength phased array laser emitted by a Dyson sphere, the entire energy output of a star can be focused onto a planet in a nearby solar system, boiling it entirely away into space in a matter of days. Such systems are known as Nicoll-Dyson beams.
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