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Conference on Lasers and Electro-Optics

Amplification without inversion in a degenerate double Lambda system

Niharika Singh, Richard D’Souza, Q. V. Lawande, B. N. Jagatap

Published Jan 1, 2012• 0 citations
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Abstract

We investigate theoretically amplification without inversion (AWI) in a degenerate double Λ system in coherently driven by two fields. We observe AWI with subnatural linewidth and attribute it to the low frequency coherence.

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Amplification without inversion: The double-Λ scheme

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Influence of field-dependent relaxation on amplification without inversion

Yevgeny V. Radeonychev, Paul Mandel, Olga A. Kocharovskaya

We study a three-level atomic system strongly driven by a monochromatic field resonant to one of atomic transitions. The second highest frequency transition is probed by a weak field. In such a system we predict a novel mechanism of probe field amplification without inversion via strong field induced spontaneous relaxation of the ground atomic state. Unlike the AWI in the (Lambda) -scheme this mechanism appears in case of sufficiently fast relaxation at the low frequency transition.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•May 10, 1996•0 citations

Amplification without population inversion in a three-level Λ-type system with an external coherent magnetic field

Hui Sun, Hong Mei Guo, Shuangli Fan +2 more

Physics Letters A•Dec 24, 2004•3 citations
We study the propagation of a bichromatic field in three-level and four-level media. In the case of a three-level medium, we consider the \ensuremath{\Lambda} configuration and demonstrate that if the upper level is not empty there is a critical value for the low-frequency coherence such that below this threshold and for intense fields, coherent bleaching occurs. This implies a sharp reduction of the field absorption and the fluorescence emission whereas above this threshold a parametric instability takes place. It corresponds to an amplification of the field that does not need a population inversion between the optical transitions. Finally we prove that the field alone cannot create a low-frequency coherence exceeding this threshold. Therefore we analyze the double-\ensuremath{\Lambda} configuration involving a four-level medium in which the upper and lower pairs of atomic levels have a low-frequency separation while optical transitions take place between the two pairs of states. An intense bichromatic field that is resonant with one upper state and the lower levels and a weak bichromatic field resonant with the other upper state and the same two lower states are sent into the medium. We analyze the limit in which the low-frequency coherence created between the lower pair of states has a relaxation time which is large. Then there will be population trapping in the lower states leading to coherent bleaching if there is no inversion between the upper levels but there will be amplification if there is inversion between the upper levels. In this way amplification at the optical transitions without population inversion between these states is realized.
The effects of incoherent pumping on the phase control of amplification without inversion (AWI) are investigated in a three-level Λ system with a weak probe field. It is shown that, similar to spontaneously generated coherence, incoherent pumping is necessary to make the system become sensitive to the relative phase. We find that the region in which AWI can be exhibited is widened with the enhancement of incoherent pumping, and that the amplitude of the probe gain can be also changed where there exists an extremum of the amplitude for a given probe detuning.