EXPERIMENTAL DEMONSTRATION OF LIGHT AMPLIFICATION WITHOUT POPULATION-INVERSION

We report the observation of light amplification without population in version. A linear superposition of an m = 1 and an m = -1 magnetic sub state is populated coherently. Absorption from this superposition to a higher state is canceled by interference of channels, a so-called dar k resonance. An inverse transition is used for amplification of light. The temporal behavior of the amplified pulse and the gain are studied as a function of the energy splitting due to a magnetic field. In a v apor of cadmium-112 gain factors of up to 4.3 are observed.