sumanth
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Theodore Maiman made the first laser operate 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.
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".
Coherence is one of the unique properties of laser light. It arises from the stimulated emission process which provides the amplification. Since a common stimulus triggers the emission events which provide the amplified light, the emitted photons are "in step" and have a definite phase relation to each other.
Coherent Light and Its Emission in Lasers. The coherent light produced by a laser differs from ordinary light in that it is made up of waves all of the same wavelength and all in phase (i.e., in step with each other); ordinary light contains many different wavelengths and phase relations.