Gain and coherence effects induced by strong cw-laser coupling in potassium–rare-gas mixtures

Abstract

We describe theoretical and experimental investigations of steady-state gain without population inversion that can occur on the D 1 transition of potassium, upon strong cw-laser excitation of the D 2 transition. A Raman-driven four-level model, in which a noninverted population in the 4 2 P 1/2 level is established via collisional transfer from the 4 2 P 3/2 level, is in good qualitative agreement with a variety of experimental results. These results include, among other studies, an examination of the impact of coherence dephasing on the realizable gain, as well as measurements of atomic energy-level populations for a case of line-center pumping that clearly displays gain. The measured relative populations for this case are n͑4P 1/2 ͒/n total ϭ0.098Ϯ0.034 and n(4P 3/2 ͒/n total ϭ0.19Ϯ0.08, where n total is the total population. These measurements indicate that the probed level 4P 1/2 population is not inverted with respect to the ground state.

Lasing without inversion

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Lasing without inversion in three-level systems without external coherent driving

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Feasibility of UV lasing without inversion in mercury vapor

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