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Journal of Optoelectronics·laser

Spontaneously Generated Coherence in an Open Four-level Atomic System

Fan Xi-jun

Published Jan 1, 2007• 0 citations
OpenAlex

Abstract

We put forward a model of an open quasi Λ-type four-level atomic system,and then investigate the effect of spontaneously generated coherence(SGC) on the gain of lasing without inversion from different respects by using the numerical calculation results of the system in the steady state.The study results show that,the switching from absorption to lasing without inversion(LWI) and the enhancement of the LWI gain can be realized by adjusting the strength of SGC;the variety of the two factors p1 to p2 which represent the SGC effect will produce remarkable different influence on the LWI gain.We also find that,the LWI gain is much larger in open system than that in the corresponding closed system;moreover,when the incoherent pump field is absent,the LWI gain can be obtained in the open system but cant in the closed system.

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The effect of spontaneously generated coherence on the gain of lasing without inversion(LWI) is studied in an open quasi-Λ type four-level atomic system with Doppler broadening from different respects.The results show that,for a fixed SGC strength,LWI gain decreases with increasing the value of the Doppler width;no matter the Doppler broadening is obvious or not,the LWI gain larger than that without SGC always can be gotten by choosing suitable value of the SGC strength,and this difference becomes more evident with the Doppler width decreasing;the atomic exit and injection rates also can dramatically affect LWI gain;a much larger LWI gain in open system than that in the corresponding closed system can be obained.

Journal of Optoelectronics·laser•Jan 1, 2008•0 citations

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Modulation role of spontaneously generated coherence in the light fields propagating

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By using the numerical calculation results of the density matrix equations of motion of a closed Λ-type inversionless lasing system,the effects of the propagation of light fields on the gain of lasing without inversion(LWI),Rabi frequencies of the probe and driving fields,and the modulation role of spontaneously generated coherence(SGC) on the effects were investigated when the Doppler broadening presents.It was shown that,with the distance increasing,LWI gain first increases and then decreases,Rabi frequency of the probe field(the driving field) increases monotonously(decreases);at a specific propagation distance,LWI gain first increases and then decreases with increasing of the Rabi frequency of the driving field at the entrance of the medium,and LWI gain decreases monotonously with increasing of the Doppler broadening width;SGC has a remarkable manipulation role on the effect of propagation of the light fields,the LWI gain with SGC is much larger than that without SGC.

Journal of Optoelectronics·laser•Jan 1, 2008•0 citations
We put forward a model of an open quasi Λ-type four-level atomic system,and then investigate the effect of spontaneously generated coherence(SGC) on the gain of lasing without inversion from different respects by using the numerical calculation results of the system in the steady state.The study results show that,the switching from absorption to lasing without inversion(LWI) and the enhancement of the LWI gain can be realized by adjusting the strength of SGC;the variety of the two factors p1 to p2 which represent the SGC effect will produce remarkable different influence on the LWI gain.We also find that,the LWI gain is much larger in open system than that in the corresponding closed system;moreover,when the incoherent pump field is absent,the LWI gain can be obtained in the open system but cant in the closed system.
The effect of spontaneously generated coherence on the gain of lasing without inversion(LWI) is studied in an open quasi-Λ type four-level atomic system with Doppler broadening from different respects.The results show that,for a fixed SGC strength,LWI gain decreases with increasing the value of the Doppler width;no matter the Doppler broadening is obvious or not,the LWI gain larger than that without SGC always can be gotten by choosing suitable value of the SGC strength,and this difference becomes more evident with the Doppler width decreasing;the atomic exit and injection rates also can dramatically affect LWI gain;a much larger LWI gain in open system than that in the corresponding closed system can be obained.
We have studied the effect of the spontaneously generated coherence (SGC) on gain of lasing without inversion (LWI) in a closed three-level Λ-type atomic system with Doppler broadening. It is shown that, regardless of the driving and probe fields being co- or counter-propagating, at a suitable value of the Doppler width, we can obtain a much larger LWI gain with SGC than that without SGC; and the region of the LWI gain spectrum with SGC is obviously larger than that without SGC. When the Doppler width takes a constant value, the gain does not monotonically decrease or increase with increasing strength of SGC, the largest LWI gain can be obtained by adjusting strength of SGC. Generally speaking, the co-propagating probe and driving fields is favourable to obtain a larger LWI gain.
The effect of spontaneously generated coherence （SGC） on transient evolution of gain of lasing without inversion （LWI） and modulation roles of the injection rate ratio and exit rate on SGC-dependent gain in an open Ladder type three level system are studied by using the numerical solution of the density matrix motion equation of the system. It was shown that: variation of SGC strength will make the transient and final stationary gains having a considerable changing; when incoherent pumping presents, LWI gain increases with the ratio of injection rates and exit rate decreasing, however, when incoherent pumping is absent, the case is just the opposite; by choosing suitable values of SGC strength, the injection rate ratio and exit rate, we can obtain the largest transient and final stationary gain.
By using the numerical calculation results of the density matrix equations of motion of a closed Λ-type inversionless lasing system,the effects of the propagation of light fields on the gain of lasing without inversion(LWI),Rabi frequencies of the probe and driving fields,and the modulation role of spontaneously generated coherence(SGC) on the effects were investigated when the Doppler broadening presents.It was shown that,with the distance increasing,LWI gain first increases and then decreases,Rabi frequency of the probe field(the driving field) increases monotonously(decreases);at a specific propagation distance,LWI gain first increases and then decreases with increasing of the Rabi frequency of the driving field at the entrance of the medium,and LWI gain decreases monotonously with increasing of the Doppler broadening width;SGC has a remarkable manipulation role on the effect of propagation of the light fields,the LWI gain with SGC is much larger than that without SGC.