The origins of laser technology go back to 1900, when Max Planck, a German theoretical physicist, discovered the relationship between energy and frequency of radiation and concluded that energy could be emitted or absorbed only in discrete chunks, named “quanta.”
In 1905, physicist Albert Einstein proposed how light delivers its energy in chunks, which are represented by photons—discrete quantum particles.1 Later, in 1916, he introduced the concept of stimulated emission: photons, by interacting with excited atoms or molecules, could stimulate the emission of new photons having the same frequency, phase, polarization and direction of the first one.
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