Laser

The principle of the continuous maser could be applied to visible wavelengths. The laser uses a ruby cylinder to emit an intense, coherent beam of red light. This invention allows for focused light that can achieve extremely high temperatures.
 Theodore Harold Maiman United States 1960 Laser

The principle of the continuous maser could be applied to visible wavelengths. The laser uses a ruby cylinder to emit an intense, coherent beam of red light. This invention allows for focused light that can achieve extremely high temperatures.