Lasing without inversion: Concepts and prospects
Conference Paper
Overview
Overview
abstract
Various noninversion lasing schemes are reviewed. One of the schemes utilizes quantum interference to obtain noninversion lasing. In his scheme the negation of absorption is due to the Fano interferences between the two upper levels through the continuum. Along these lines the authors have investigated the utilization of the quantum interference phenomenon to cancel absorption by means of the quantum beat laser concept. They have recently shown that the quantum beat laser can yield stimulated emission in a configuration involving two lower levels and one upper level. It is possible to partially or totally cancel the absorption due to the coherence between the ground state doublet. The linear analysis and the cancellation of absorption have been investigated in the following situations. (1) The atoms are transit time broadened, and the atomic coherence is due to initial preparation. (2) The atoms decay via radiation, and the atomic coherence is due to initial preparation. (3) The atomic coherence is induced by microwave radiation. (4) The coherence is produced by a coherent Raman process. In each of the above situations the authors considered both nondegenerate and degenerate cases in which the laser operates, first, on two different frequencies as in the quantum beat laser and, second, on one frequency which is equally detuned from the ground states.
