【作者】 白艳锋；

【导师】 郭弘；

【作者基本信息】 华南师范大学 ， 光学， 2005， 硕士

【摘要】 本论文就三能级系统中与量子相干相关的一些现象,如无反转激光(Lasing Without Inversion,LWI),慢光速和超光速(Subluminal and Superluminal)等给出了系统的理论研究.论文中对实现LWI模型的提出、影响LWI产生的一些基本参量、光脉冲从慢光速到超光速的传播(光开关)等都作了基本的分析。论文内容及结论共分为四个部分:第一部分为前言;第二部分对光场与物质相互作用的半经典理论作了简单的回顾;第三部分对量子相干中的一个重要现象:电磁感应透明(Electromagnetically Induced:Transparency, EIT)进行了具体的分析,同时,对它的两个重要应用:LWI,慢光速和超光速给出了简单的介绍;随后三个部分主要是介绍作者在硕士研究生期间所做的工作。 第一部分是前言,介绍了本论文的研究背景和研究目的。 在第二部分中,本论文以两能级原子为例,介绍了光与原子介质相互作用的半经典理论,这一理论为下面的工作提供了理论基础。 第三部分在光与物质相互作用半经典理论的基础上,推导出量子相干中一个极其有趣的现象:EIT,其中着重分析了它产生的机制和潜在的应用。在这些应用中,重点分析了我们感兴趣的LWI,慢光速和超光速现象, 接下来的一部分主要分析三能级原子系统中的LWI。这里,为了实现LWI,我们提出了一个新的模型。以往的模型需要引入非相干的泵浦(incoherent pumping),或者考虑两个激发态之间的衰减,在我们的模型中,仅仅考虑了两个上能级之间的自发诱导相干(spontaneously generated coherence,SGC),同样实现了无反转激光。但整个过程中,SGC项并不总是推动LWI的出现,有时它可能会阻碍LWI的实现。同时我们也发现探测场的产生不仅仅是因为它本身,另外一个驱动场同样起了作用,这种现象可能是一种新的相干现象。 在第五部分,我们对出现LWI的原子系统中非相干泵浦的作用给出了新的分析。通过数值模拟的结果,我们发现,在使系统变得依赖于相对相位的过程中,非相干泵浦同SGC同样不可缺少。而且存在一个非相干泵浦,它对应于探测增益振幅的最大值。更多还原

【Abstract】 The thesis focused on the systematically theoretical study on some phenomena about quantum coherence: Lasing without inversion (LWI), subluminal and superluminal et al.. Firstly, we proposed a new three-level model used to realize LWI, in which we analyzed some basic parameters which can affect the realization of LWI. Secondly, we investigated the change of the group velocity from subluminal to superluminal (optic knob). This paper is organized as six sections according to the contents and results: section 1 is a survey; section 2 is a review on the semiclassical theory of light-matter interaction; in section 3, Electromagnetically induced transparency (EIT) which is an interesting phenomenon about quantum coherence is investigated. At the same time, LWI, subluminal and superluminal, as two important application of EIT, are simply introduced; The following three sections are the introductions of the author’s work.In the first Chapter, We give an introduction of the research background and the research purpose of my thesis.In Chapter 2, Taken the two-level atomic system for example, the semiclassical theory of laser-matter interaction, which is the basis of the following works.In Chapter 3, Based on the semiclassical theory of light-matter interaction, we get EIT, an interesting phenomenon about quantum coherence. Here, we emphasize its production mechanism and application. During the application, we focus on LWI, subluminal and superluminal, which we are interested in.In the following Chapter, we mainly analyze the phenomenon of LWI in a three-level system. Here, we propose a new three-level model used to realize LWI. The incoherent pumping or the decay between two upper levels must be considered in others’ models. While, in our model, we can realize LWI only when spontaneously generated coherence (SGC) between two upper levels is considered. During this process, SGC term is not always impulse the occurrence of LWI, it can cumber the realization under some condition.At the same time, we also find that the generation of the probe field is not only due to itself, but also to another driving field, this can be viewed as a new coherence.In Chapter 5, we again investigate the effects of the incoherent pumping in a three-level system used to realize LWI. We find that, by the numerical results, both the incoherent pumping and SGC are necessary in the process of making the system become sensitive to the relative phase. Here, there exists an incoherent pumping corresponding to the extremum of the amplitude of the probe gain.In the last chapter, the change of the group velocity is discussed in a V system. We find that the change of incoherent pumping can affect the slope of the dispersive curves. Here, there exists an incoherent pumping rate which makes the group velocity reach the extremum. The existence of SGC is just the cause for the occurrence of the extremum. During the whole process, SGC can be regarded as a optic knob which is used to manipulate light propagation from subluminal to superluminal.更多还原