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Acta Physica Sinica

Effect of spontaneously generated coherence on transient evolution of LWI gain in an open Ladder type system

Yanling Yang, Lei Wang, Liu Zhong-Bo, Lu Hong-Wu, Fan Xi-jun, (1)山东师范大学传播学院，济南 250014; (2)山东师范大学物理与电子科学学院，济南 250014

Published Jan 1, 2009• 7 citations
Publisher

Abstract

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.

DOI
10.7498/aps.58.3161

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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.
In this paper we study the influence of spontaneously generated coherence (SGC) on propagation effect and the modulation role of the atomic exit rate(r0)and ratio(S) of the atomic injection rates on the SGC-dependent propagation effect in an open V-type three-level lasing without inversion(LWI) system with Doppler broadening,by using the calculation results of the density matrix motion equations and the propagation equations of the driving and probe fields,in order to get larger LWI gain and intensity of the probe field.It is shown that with propagation distance increasing,LWI gain and Rabi frequency(intensity) of the probe field first increase and then decrease,while the Rabi frequency(intensity) of the driving field decreases monotonously;LWI gain and Rabi frequency(intensity) of the probe field increase with SGC strength(measured by θ) increasing.When θ=π,we can obtain the largest LWI gain and Rabi frequency(intensity) of the probe field;in the case with SGC,we can get much larger LWI gain and Rabi frequency(intensity) of the probe field than those in the case without SGC.In certain value ranges of r0 and S,LWI gain and Rabi frequency(intensity) of the probe field increase with r0 and S increasing.By choosing proper values of γ0 and S,in the open system we can obtain much higher LWI gain and Rabi frequency(intensity) of the probe field than those in the corresponding 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.
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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.
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