Lasing without inversion

[2] A laser working under this scheme exploits the quantum interference between the probability amplitudes of atomic transitions in order to eliminate absorption without disturbing the stimulated emission.

[3] This phenomenon is also the essence of electromagnetically induced transparency.

[4] The basic LWI concept was first predicted by Ali Javan in 1956.

[5][6] The first demonstration of LWI was carried out by Marlan Scully in an experiment in rubidium and sodium at Texas A&M University, and then at NIST in Boulder.

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