The word LASER is actually an acronym for Light Amplification by Stimulated Emission of Radiation. A laser emits light through a process of optical amplification based on the stimulated emission of photons.
In 1917, Albert Einstein established the theoretic foundations for the laser and the maser in the paper “On the Quantum Theory of Radiation” based on Planck’s law of radiation. In 1928, Rudolf W. Ladenburg confirmed the existences stimulated emission and negative absorption.
In 1959, Charles Townes and Arthur Schawlow were granted a patent for the maser which was used to amplify radio signals and as an ultrasensitive detector for space research.
In 1958, Charles Townes and Arthur Schawlow theorized and published papers about a visible laser, an invention that would use infrared and/or visible spectrum light. The first operating laser was made by Theodore Maiman on 16 May 1960 at the Hughes Research Laboratory in California by shining a high-power flash lamp on a ruby rod with silver-coated surfaces.
In 1960, lasers were called “a solution looking for a problem”. Since then lasers have been used in thousands of varied applications in every part of society, including consumer electronics, information technology, science, medicine, industry, law enforcement, entertainment, and the military. (Wikipedia)