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Physical Review A

Lasing without inversion: Theory of transient behavior

Victor R. Blok, Gennady M. Krochik

Published Aug 1, 1991• 20 citations
Publisher

Abstract

We present consistent transient theory of lasing without inversion and show by numerical analysis that pulse-mode lasing is feasible in a two-level system with split upper levels coupled by an external high-frequency electromagnetic field.
DOI
10.1103/physreva.44.2036

Related papers

Feasibility of lasing without inversion in the two-level system with split upper levels coupled by microwave radiation

Victor R. Blok, Gennady M. Krochik

Zhu, Cresser, and Fearn [preceding Comment, Phys. Rev. A 43, 5170 (1991)] give an erroneous formal proof that lasing without inversion in the system with two upper optically identical levels is impossible. Their approach has little to do with the case of two close but different, well-separated split levels, considered in our previous paper [Blok and Krochik, Phys. Rev. A 41, 1517 (1990)]. It is evident even without laborious calculation that lasing without inversion is impossible in the system of indistinguishable levels, considered by Zhu, Cresser, and Fearn, because one cannot provide the interference among identical transitions. Their formal proof is, in addition, incorrect because they apply a steady-state approximation to the conditions where it is not valid; the transient response of the medium must be calculated instead. We also used the steady-state approximation in our previous paper, but very cautiously, in a domain where it is valid to obtain some analytical formulas, which proved to be qualitatively correct under the transient response approach [Blok and Krochik (unpublished)].

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Comment on ‘‘Theory of lasers without inversion’’

Shi-Yao Zhu, James D. Cresser, H. Fearn

We prove that lasing without inversion is impossible in the three-level system with two active upper levels that are mixed by applied low-frequency electromagnetic radiation. Such lasing was recently proposed by Blok and Krochik [Phys. Rev. A 41, 1517 (1990)].

Physical Review A•May 1, 1991•2 citations

Theory of lasers without inversion

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We here present the theory of lasing without inversion for systems with a split upper laser level. We show that the effect of amplification without inversion may be realized for at least two different situations. In the first situation, the effect is due to the asymmetry of radiative characteristics of quasidegenerate transitions. In the second situation, the effect can be provided without any asymmetry and is achievable for the definite phase of the transfer of coherence between the quasidegenerate levels (quasiparametric amplification). We also show that for laser amplification without inversion, the rate (frequency) of mixing of the quasidegenerate levels should be significantly higher than the linewidths of these levels. This mixing of quasidegenerate levels can be realized by low-frequency electromagnetic radiation or by interaction with an auxiliary third level. In addition, we derive the conditions for providing laser action for such systems rigorously, and we give some specific examples for the realization of this effect in gaseous and solid-state media. One of the most promising configurations may be realized in solid-state media when two narrow quasidegenerate levels are embedded in quasifree states (low-density state conduction band). We also discuss the use of a parametric mechanism for the creation of spatial gratings and for the construction of new types of electro-optical devices.

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Effects of the upper level coupling field on lasing without inversion in a V-type system

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Nonlinear theory of lasers without inversion with two upper lasing levels

Shi Yao Zhu, Ernst E. Fill

The nonlinear equation of motion for the laser field is obtained by using a perturbation method up to third order. The linear gain and intensity of the laser field are obtained. A perfect lasing without inversion can be achieved when ${\mathrm{\ensuremath{\delta}}}_{3}$${\mathrm{\ensuremath{\mu}}}_{2}$ \ensuremath{\surd}${\mathrm{\ensuremath{\Gamma}}}_{2}$ =-${\mathrm{\ensuremath{\delta}}}_{2}$${\mathrm{\ensuremath{\mu}}}_{3}$ \ensuremath{\surd}${\mathrm{\ensuremath{\Gamma}}}_{3}$ .

Physical Review A•Nov 1, 1990•34 citations
Zhu, Cresser, and Fearn [preceding Comment, Phys. Rev. A 43, 5170 (1991)] give an erroneous formal proof that lasing without inversion in the system with two upper optically identical levels is impossible. Their approach has little to do with the case of two close but different, well-separated split levels, considered in our previous paper [Blok and Krochik, Phys. Rev. A 41, 1517 (1990)]. It is evident even without laborious calculation that lasing without inversion is impossible in the system of indistinguishable levels, considered by Zhu, Cresser, and Fearn, because one cannot provide the interference among identical transitions. Their formal proof is, in addition, incorrect because they apply a steady-state approximation to the conditions where it is not valid; the transient response of the medium must be calculated instead. We also used the steady-state approximation in our previous paper, but very cautiously, in a domain where it is valid to obtain some analytical formulas, which proved to be qualitatively correct under the transient response approach [Blok and Krochik (unpublished)].
We here present the theory of lasing without inversion for systems with a split upper laser level. We show that the effect of amplification without inversion may be realized for at least two different situations. In the first situation, the effect is due to the asymmetry of radiative characteristics of quasidegenerate transitions. In the second situation, the effect can be provided without any asymmetry and is achievable for the definite phase of the transfer of coherence between the quasidegenerate levels (quasiparametric amplification). We also show that for laser amplification without inversion, the rate (frequency) of mixing of the quasidegenerate levels should be significantly higher than the linewidths of these levels. This mixing of quasidegenerate levels can be realized by low-frequency electromagnetic radiation or by interaction with an auxiliary third level. In addition, we derive the conditions for providing laser action for such systems rigorously, and we give some specific examples for the realization of this effect in gaseous and solid-state media. One of the most promising configurations may be realized in solid-state media when two narrow quasidegenerate levels are embedded in quasifree states (low-density state conduction band). We also discuss the use of a parametric mechanism for the creation of spatial gratings and for the construction of new types of electro-optical devices.
The nonlinear equation of motion for the laser field is obtained by using a perturbation method up to third order. The linear gain and intensity of the laser field are obtained. A perfect lasing without inversion can be achieved when ${\mathrm{\ensuremath{\delta}}}_{3}$${\mathrm{\ensuremath{\mu}}}_{2}$ \ensuremath{\surd}${\mathrm{\ensuremath{\Gamma}}}_{2}$ =-${\mathrm{\ensuremath{\delta}}}_{2}$${\mathrm{\ensuremath{\mu}}}_{3}$ \ensuremath{\surd}${\mathrm{\ensuremath{\Gamma}}}_{3}$ .