Coherent Control Study Of Propagation Effect And Transient Evolution Of Lasing Without Inversion In An Open V-type Three-level System

The study of coherent control of optical properties and optical process is one of theimportant and active research front fields in international optics nowadays. The study ofcoherent control has not only an important theoretical value, but also wide applicationprospects in many fields, such as nonlinear optics, quantum optics, photo-communication, andquantum information etc. The quantum coherence and interference of the atomic system canlead to many important physical phenomena, in which lasing without inversion (LWI) hasreceived enormous interest and tremendous attention. LWI can obtain laser light in spectraldomains where conventional methods based on population inversion are difficult or notavailable to implement, so the study of LWI has not only an important theoretical value, butalso wide application prospects.Based on the work of the former people, we studied the coherent control of propagationeffect and transient evolution of lasing without inversion in an open V-type three-level systemin this paper. This paper consists of four chapters.In Chapter 1, we explained the research background and significance for studying LWIand coherent control, showed the basic principle of producing LWI, and introduced thecurrent research state of the coherent control and LWI.In Chapter 2, we studied the influence of spontaneously generated coherence (SGC) onLWI propagation effect in an open V-type three-level atomic system for both cases with andwithout Doppler broadening, and compared this with that in the corresponding closed system.We found that: LWI gain and Rabi frequency (intensity) of the probe field (i.e. LWI) increasewith SGC strength (measured byθ) increasing, whenθ=π, we can obtain the largestLWI gain and intensity; in the case with SGC, we can get LWI gain and Rabi frequency(intensity) of the probe field much larger than those in the case without SGC; in certain valueranges ofr0 and S , LWI gain and Rabi frequency (intensity) of the probe field increase with r0 and S increasing; by choosing proper values ofr0 and S, in the open system we can obtainLWI gain and Rabi frequency (intensity) of the probe field much higher than those in thecorresponding closed system; in the case with Doppler effect，the propagation distance inwhich LWI gain exists is longer than that in the case without Doppler broadening, the largestvalue of LWI gain is smaller than that without Doppler effect; but largest value of Rabifrequency (intensity) of the probe field is larger than that without Doppler effect..In Chapter 3, based on the work of chapter 2, we investigated mainly control role of therelative phase (Φ) between the probe and the driving fields on propagation effect in aDoppler broadening open V-type system with SGC. It is shown that the relative phase (Φ)has remarkable periodical influence on the propagation effect, and the period is 2π；byselecting appropriate value ofΦ, we can get larger lasing without inversion (LWI) gain andlonger propagation distance in which gain existing, and hence obtain higher probe field (i.e.LWI) intensity. In addition, the atomic exit rate (r0 ) and ratio (S) of the atomic injection ratesalso have a considerable modulation role on the phase-dependent propagation effect. Incertain value range of S（r0）, with value of S（r0）increasing, LWI gain and intensity increase andthe propagation distance needed for reaching at the intensity maximum value becomes longer;the largest values of LWI gain and intensity and the propagation distance in which the gainexisting in the corresponding closed system are smaller than those in the open system. TheDoppler effect also has an obvious influence on spatial evolution of LWI gain and intensity.In Chapter 4, Using the numerical result of the density matrix motion equations of theopen V-type three-level atomic system, we had analyzed control role of the relative phasebetween the probe and driving fields on transient evolution of gain of lasing without inversion(LWI) and modulation role of ratio of the atomic injection rates and atomic exit rate on thephase-dependent transient evolution in both cases without and with an incoherent pump. It isshown that: Regardless of that the incoherent pump is present or not, changing value of therelative phase has a significant effect on the transient evolution of the gain.The gain transientevolution curve when the incoherent pump is present is similar to that when the incoherentpump is absent; but comparing with the case with the incoherent pump, when the incoherentpump is absent, the times needed for getting the largest transient gain and steady gain are longer, the oscillation amplitude in the evolution process is larger, and gain is also larger.