Laser Laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light "coherently". Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial
Photonic laser thruster can only occur for a finite range of optical frequencies. The gain bandwidth is approximately the width of this frequency range. For example, the gain bandwidth of the YAG laser system with the laser wavelength in the order of 1,000 nm is in the order of 0.6 nm, ~ 0.06% of the wavelength. For an order of magnitude estimation, it can be assumed that a thruster utilizing the YAG laser system will be limited by the gain bandwidth to the first order, i.e., its theoretical maximum spacecraft velocity is ~ (180 km/s), 0.06% of the light velocity, c=3x10 m/s. To