laser
... LASER stands for Light Amplification by the Stimulated Emission of Radiation. All the fundamental principles underlying the operation of the laser were established by Albert Einstein in 1916. However, the first working laser was constructed by an American scientist Theodore Maiman in 1960. ... A laser produces coherent waves. All the light waves produced by a laser have same wavelengths, travel in the same direction, have same frequency and they are in phase with each other.