Albert Einstein, as so often seems to happen in physics, wrote the equations behind the laser.
In 1917, having wrapped up his theory of gravity, Einstein proposed the idea of "stimulated emission," taking advantage of the property of atoms to emit light of one frequency (the light we see from the sun or a light bulb is a many-colored mix of wavelengths and frequencies) when they are struck by light.
Albert Einstein, not Darth Vader, first imagined laser technology - USATODAY.com