Free Electron Lasers
In the early 21st century, humanity developed the first high powered lasers that did not require a magazine of chemicals, solid or gas state mediums to generate a laser beam. Instead free electron lasers use an accelerated electron beam as the physical lasing medium. As such, since an FEL does not depend on expendable fuel mediums, it can continue to operate as long as it has a source of electrical power. The nature of using an electron beam means it can also be adjusted to tune the output laser beam to a wide range of EM frequencies, Microwaves, visible light, or infrared and ultra violet.