【作者】 乔红霞；

【导师】 樊锡君；

【作者基本信息】 山东师范大学 ， 理论物理， 2008， 硕士

【摘要】 物质的光学性质和光学过程的相干控制的研究是当前国际上光学研究中重要而活跃的前沿领域之一。相干控制的研究不仅有重要的理论意义,而且在量子光学、非线性光学、量子信息和光通讯等领域内都有重要的应用价值。原子相干现象和量子干涉效应在很多方面都具有潜在的应用价值,而在众多的原子相干和量子干涉现象中,无粒子数反转激光(Lasing Without Inversion简称LWI)引起了人们更大的兴趣和特别的重视。作为一种产生激光的新型机制,应用无粒子数反转激光可以在应用传统激光理论和方法很难甚至不可能产生激光的高频光谱区(X-射线甚至γ-射线区)产生激光,因此无粒子数反转激光的研究不仅具有重要的理论价值而且具有广阔的应用前景。本论文在前人研究工作的基础上,对Λ型三能级系统无反转激光相干控制的理论进行了研究,全文内容共分四章:第一章综述,阐述了光学性质相干控制和无粒子数反转激光的研究意义、无粒子数反转激光产生的物理机制,并介绍了当前这一重要课题的研究现状。第二章存在和不存在Doppler效应两种情况下,对封闭的Λ型三能级无反转激光系统受光场传播的影响以及自发辐射诱导相干对这个影响显著调制的研究。不考虑Doppler效应时,讨论了不同θ值下,探测场激光增益Imρ31、驱动场Rabi频率Ωc和探测场Rabi频率Ωp、粒子数差ρ33 -ρ11分别随传播距离的变化关系,并讨论了特定传播距离处(z=10cm)探测场激光增益随激光介质入口处驱动场Rabi频率的变化关系;考虑Doppler效应情况下,在驱动场、探测场和原子运动均同向时讨论了不同θ值探测场激光增益Imρ31、驱动场Rabi频率Ωc和探测场Rabi频率Ωp、粒子数差ρ33 -ρ11分别随传播距离的变化关系,特定传播距离处(z=10cm)探测场激光增益分别随介质入口处驱动场Rabi频率和Doppler展宽的变化关系。研究表明,存在Doppler效应与否,皆有LWI增益随着传播距离的增加先增大后减小,探测场Rabi频率随着传播距离的增加而增大,驱动场的Rabi频率随传播距离的增加而减小;特定传播距离处,LWI增益随介质入口处驱动场Rabi频率的增加先增大后减小。存在Doppler效应时,LWI增益随Doppler展宽值的增加单调减小。第三章在第二章的基础上,研究了具有自发辐射诱导相干的封闭的Λ型三能级系统中,探测场和驱动场之间的相对位相(Φ)对探测增益驱动场Rabi频率和探测场Rabi频率、粒子数差分别随传播距离变化的控制作用。研究表明,当Φ=0(即仅考虑SGC效应)时可获得LWI增益,但增益较小;当Φ=π/4和Φ=π/2时LWI增益较大。另外还研究了特定传播距离处,对应不同的Φ值,LWI增益与介质入口处的驱动场Rabi频率和Doppler展宽的关系。第四章利用数值计算结果研究了存在自发辐射诱导相干开放的Λ型无反转激光系统相对位相Φ的变化对原子响应的瞬态演化规律的影响。我们发现:不存在非相干泵浦的情况下,对一定的相对位相值瞬态和稳态将呈现对探测场的电磁感应透明(EIT),特别是原子注入速率比和原子退出速率的变化都将对与位相有关的增益瞬态演化规律有显著的调制作用。研究还表明,与不存在非相干泵浦时相比,除了相对位相Φ=0(π)的情况外当存在非相干泵浦时系统可得到大得多的稳态增益(吸收),而达到稳态所需的演化时间也短得多;初始条件的变化不改变稳态增益(吸收)的大小但对瞬态演化过程有明显的影响。更多还原

【Abstract】 The study of coherent control of optical properties and optical courses is one of the most important and active research front fields in international optics nowadays. The study of coherent control has not only an important theoretical value, but also wide application prospects in many fields, such as quantum optics, nonlinear optics, quantum information and optical communication, etc. In addition, atomic coherence and quantum interference effects have multiple potential applications in many aspects. Among numerous phenomena of atomic coherence and quantum interference, lasing without inversion (LWI) has received tremendous attention. As a new mechanism of producing laser, LWI can obtain laser light spectral domains, e.g. the x-ray evenγ-ray range, where conventional methods based on population inversion are not available or are difficult to implement, so the study of LWI has not only an important theoretical value, but also wide application prospects.Based on the work of the former people, we mainly studied the coherent control of optical properties in aΛ-type three-level system of lasing without inversion. This paper consists of four chapters.In Chapter 1, we explained the significance for studying coherent control and LWI, showed the basic principle of producing LWI, and introduced simply the current research state of coherent control and LWI, and the main contents for the important study subject at present.In Chapter 2, we studied the effect of propagation of fields on lasing without inversion and the modulation role of spontaneously generated coherence on this effect in a closedΛ-type three-level system with or without the Doppler effect, respectively. Ignoring the Doppler effect, we discussed the effects of the propagation of fields on the LWI gain, Rabi frequencies of the driving and probe fields, the population difference for different values ofθ. We also studied the relationship between the LWI gain at the specific distance and the Rabi frequency of the driving field at the entrance of the medium for different values ofθ. Considering the Doppler effect, we analyzed the effects of the propagation of fields on the LWI gain, Rabi frequencies of the driving and probe fields, the population difference for different values ofθwhen the probe and driving fields and atomic motion are co-propagating. We also studied the relationships between the LWI gain at the specific distance and the Rabi frequency of the driving field at the entrance of the medium, Doppler broadening width whenθtakes different values. It is shown that: regardless of the existence of the Doppler effect, LWI gain increases first and decreases afterwards, Rabi frequency of the probe field increases and the Rabi frequency of the driving field decreases with the distance increasing. At a specific distance, LWI gain increases first and decreases afterwards with the Rabi frequency of the driving field at the entrance of the medium increasing. Considering the Doppler effect, the LWI gain decreases monotonously with the Doppler broadening width increasing.In Chapter 3, based on the work of chapter 2, we investigated the control role of the relative phase (Φ) between the probe and driving fields on the LWI gain, Rabi frequencies of the driving and probe fields, the population difference during the propagation process in a closedΛ-type system with spontaneously generated coherence (SGC). WhenΦ=0, i.e. when only SGC is considered, LWI gain can be obtained, but the LWI gain is less; whenΦ=π/4andΦ=π/2, larger LWI gain can be obtained. We also studied the relationships between the LWI gain at a specific distance and the Rabi frequency of the driving field at the entrance of the medium, Doppler broadening width when the relative phase takes different values.In Chapter 4, we studied the effects of the relative phase,Φ, between the probe and driving fields on the transient evolution rule of the atomic response in an openΛ-type inversionless lasing system with spontaneously generated coherence by numerical results. We found that: when the incoherent pumping is absent, electromagnetically induced transparency (EIT) can occur. Specially, varying the atomic exit rate and ratio of the atomic injection rates can remarkably modulate the transient evolution rule of the phase–dependent gain. It is also shown that under the same conditions, the values of the LWI gain with incoherent pumping are evidently larger than those without incoherent pumping exceptΦ=0(π) and the time reaching the steady state is shorter; varying the initial condition doesn’t change the stationary value of the LWI gain but can remarkably affect the transient evolution process of the LWI gain.更多还原