= Lasing without inversion
{wiki=Lasing_without_inversion}
Lasing without inversion (LWI) is a phenomenon in quantum optics that refers to a mechanism of producing coherent light (laser light) in a system where the usual requirement for population inversion is not met. Normally, in traditional laser operation, a population inversion is necessary, where more atoms or molecules are in an excited state than in a lower energy state. This population inversion is essential for achieving stimulated emission, the fundamental process that amplifies light in a laser.
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