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Quantum Electronics and Laser Science Conference

Amplification without inversion in a multilevel medium

Paul Mandel, Olga A. Kocharovskaya

Published May 12, 1991• 0 citations
OpenAlex

Abstract

In a two-level medium, the condition for amplification is population inversion. The simplest scheme in which inversionless amplification occurs is a three-level medium. It was shown recently that a trichromatic field can be amplified by a three-level medium without population inversion if the low-frequency (LF) coherence exceeds some critical value.1 The question that we address here is how to generalize the two-level amplification condition when one or both levels are split into a number of sublevels.

Related papers

Inversionless amplification of a monochromatic field by a three-level medium

Paul Mandel, Olga A. Kocharovskaya

We consider a three-level medium with low-frequency separation between the two upper levels. The medium interacts with an external field that induces a coherence between the two upper levels. We analyze the amplification condition for the probe monochromatic optical field in a general nonresonant case. We show that amplification without population inversion arises either at line center or at the sidebands, depending on the sign of the population difference between the upper sublevels. This amplification occurs in a limited range of the coherent pump intensity.

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Inversionless amplification in a multilevel system

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We prove that the amplification condition for a multifrequency field in an atomic system with multiple splitting of the operating levels implies a population inversion between the eigenstates of the density matrix. This explains the possibility of amplification without population inversion when a coherent superposition state of sublevels is prepared.

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Amplification without inversion in a three-level medium

Olga A. Kocharovskaya, Paul Mandef, Shuban Zhang

An attractive idea that has been widely discussed recently is to convert a low-frequency (LF) coherent input into a high-frequency coherent output without population inversion in tire medium.1-3 The simplest scheme for realizing this idea is a three-level medium in which a microwave field acts on tire LF transition and amplification occurs at either one or both optical transitions.

Quantum Electronics and Laser Science Conference•May 12, 1991•0 citations

Amplification without inversion: The double-Λ scheme

Olga A. Kocharovskaya, Paul Mandel

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.

Physical Review A•Jul 1, 1990•308 citations

Inversionless amplification in a three-level medium

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

We study all possible resonant three-level configurations where a low-frequency coherent pump can be converted into a high-frequency field in the absence of population inversion at both atomic high-frequency transitions. We identify two different mechanisms that provide such inversionless amplification.

Physical Review A•Feb 1, 1992•115 citations

Inversionless amplification of a monochromatic field in a nonresonant three-level ∧ medium

龚尚庆, 徐至展

A three-level medium is the simplest and most suitable model for understanding the physical mechanisras of amplification without inversion (AWI). Various analyses were presented for all possible resonant three-level configurations. Recently, P. Mandel et al. have studied the AWI in three-level ∧ model for general nonresonant case and obtained the condition for establishing AWl. In our note the inversionless amplification of a monochromatic field in a nonresonant three-level ∧ medium will be investigated.

Chinese Science Bulletin•Jan 15, 1995•1 citation
In a two-level medium, the condition for amplification is population inversion. The simplest scheme in which inversionless amplification occurs is a three-level medium. It was shown recently that a trichromatic field can be amplified by a three-level medium without population inversion if the low-frequency (LF) coherence exceeds some critical value.1 The question that we address here is how to generalize the two-level amplification condition when one or both levels are split into a number of sublevels.
We consider a three-level medium with low-frequency separation between the two upper levels. The medium interacts with an external field that induces a coherence between the two upper levels. We analyze the amplification condition for the probe monochromatic optical field in a general nonresonant case. We show that amplification without population inversion arises either at line center or at the sidebands, depending on the sign of the population difference between the upper sublevels. This amplification occurs in a limited range of the coherent pump intensity.
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.
A three-level medium is the simplest and most suitable model for understanding the physical mechanisras of amplification without inversion (AWI). Various analyses were presented for all possible resonant three-level configurations. Recently, P. Mandel et al. have studied the AWI in three-level ∧ model for general nonresonant case and obtained the condition for establishing AWl. In our note the inversionless amplification of a monochromatic field in a nonresonant three-level ∧ medium will be investigated.