【作者】 马瑞琼；

【导师】 李永放；

【作者基本信息】 陕西师范大学 ， 光学， 2006， 硕士

【摘要】 研究相干瞬态过程对理解光与物质相互作用的动力学过程非常重要,随着人们对原子相干效应认识的不断深入,探索更多更有应用前景的相干效应成为该领域研究的焦点。本文从理论上研究了三能级体系的相干效应及非相干光对相干瞬态过程的高分辨率测量。论文主要分为三个部分,第一部分主要研究了强泵浦弱探测场激发下的梯形三能级系统相干瞬态过程的特点;第二部分研究了类∧型三能级体系中相干瞬态过程的高分辨率测量及相干控制;第三部分研究了瑞利型增强瞬态四波混频的外差探测。 第一部分 利用强泵浦弱探测场研究梯形三能级系统相干瞬态过程的特点。 首先系统地研究了无啁啾脉冲所激发的相干瞬态过程中的量子干涉效应。通过对终态布居数在瞬态过程中演化的数值模拟,结合驻相法,得到了由不同通道跃迁产生的量子干涉在终态布居中形成的条纹,其中(Ⅰ)类干涉类似于多光子跃迁的干涉,(Ⅱ)类干涉类似于Ramsey干涉,(Ⅲ)类干涉则是前两类干涉的交叉作用的结果。文中详细讨论了三类干涉产生的物理机制,并结合对三类干涉条纹的比较,分析了量子干涉效应中粒子布居数的动力学演化的特点。其次研究了强啁啾脉冲所激发的相干瞬态过程的特点。通过分析啁啾对缀饰态本征能量的影响,可以得到两低能态间发生绝热布居反转的条件,结合该条件我们详细讨论了啁啾对量子干涉效应的影响,并发现可以通过控制啁啾来选择激发通道,进而实现对粒子布居的控制。最后通过对布居时域演化的模拟分析了共振跃迁振幅与离共振跃迁振幅间的量子干涉效应。 在本章的最后我们采用了一个简化的物理模型分析(Ⅰ)类干涉,基于相关理论得到了终态布居解析解。通过对解析解的分析,可以得到量子干涉所产生的条纹的周期及线型函数,它与3.3节的数值模拟恰能互相补充,能够提供相干瞬态过程中的量子干涉效应的完整信息。 第二部分 利用双延时脉冲研究类∧三能级体系的相干瞬态过程的高分辨率测量和相干控制 本文提出了一种利用非相干双延时脉冲测量两相距很近的低能态间距的方法。基于相关理论得到的布居调制周期与能态间距的明确关系,从理论上支持了更多还原

【Abstract】 The coherent transient is very important in understanding the dynamical behavior of the light-matter interaction . In this paper, the coherent transient in the three-level atom system and ultrahigh resolution transient measurement with incoherent light have been discussed theoretically . The paper is divided into three parts: In the first part , we have investigated a class of coherent transients in a ladder three-level system in the so-called pump-probe configuration , where the time-dependent response of a weak-probe limited field has been studied under a strong pump field . In the second part, ultrahigh resolution coherent transient measurements with incoherent light in the three-level A -like system and coherent control have been investigated . Finally , we have presented a new method of optical heterodyne-detection to study Rayleigy-enhanced transient four wave mixing .Part One:Quantum interference effects which were excited by a strong pump pulse and a weak probe pulse, have been investigated in a ladder three-level atom system systematically. The numerical results using the method of stationary phase shows the interference fringes in spectral , which can accurately predict the amplitudes of the frings . To describe the frings more accurately , we use the simplified treatment that it ignores the time evolution of the energy level. Based on the field-correlation theory, analytic representation of the population of final state was obtained, the character of the fringes such as period and shape can also be predicted accurately. We also describe theoretically the temporal evolution of the excited state population induced by chirped pump pulse , and find that we can control the population by manipulating the chirped pulse.Part Two:A novel approach to measure the spacing of two close energy states with two incoherent light was presented . Based on the principle of field-correlation , we obtained a analytic representation for population of the final state and the numerical results verified the feasibility of this approach . Comparing the results which were got from two defferent modle of the excited field, it was found that accurate measurement in temporal needs very wide laser spectral band , at least a half of the state spacing . If the laser spectral cannot overlap the two close states , exciting the atom at the middle of them is demanded to realize the accurate measurement.It was also found that the population can be controlled by using two time-delayed pulses . When two pulses overlapped completely , the population trap was obtained in two lower states through fixing the relative phase difference between the two pulses at odd times of n. The informations about the life of coherent state can also be gotten from the time evolution of the population in the final state .Part Three:A closed-form solution of the difference-frequency beats and the representation of third-order susceptibility for Rayleigh-enhanced four wave mixing were obtained by the method of optical heterodyne-detection. The numerical results illustrate that the method can keep the information of Rayleigh-enhanced polarization completely. And the physical analysis of the difference based on three Markovian stochastic models were also given in paper.更多还原