【作者】 李家华；

【导师】 吴颖；

【作者基本信息】 华中科技大学 ， 光学， 2007， 博士

【摘要】 本文主要研究量子相干介质中的非线性光学性质及其应用,更确切地说是在冷原子介质和半导体量子阱材料中,对光学非线性的增强效应、超慢光孤子、高效混频转换、光学双稳和多稳态的控制、自发辐射谱线的相干调控以及光在稀薄和稠密冷原子介质中的动力学性质作了理论研究。主要内容有:(1)阐述了仅利用一个低强度脉冲激光辐射,在一种长寿命增宽的三能级冷原子介质中超慢亮暗光孤子的有效生成。(2)研究了在三能级V型原子介质中借助一个微波共振辐射,二激光脉冲间非线性转化的潜在性。结果表明当一个弱泵浦激光脉冲被运用时,微波驱动场的出现能够导致具有高转化效率新激光脉冲的参量生成。(3)分析了在一个普通N型原子系统中混合吸收色散型的光学双稳态和多稳态,该系统通过一个单向环形腔由一个简并探测场和一个相干耦合场激发。发现光学双稳态可以通过调节这个耦合场的强度和频率失谐来控制,而多稳态能够在合适的频率失谐情况下被观测到。还探讨了原子合作参数对光学双稳态性质的影响。(4)分析了具有非对称双量子阱系统的介质,受到一个单向循环腔内的探测激光场的相干驱动,发生带间跃迁,产生可调谐的Fano型干涉时,吸收-色散混合型光学双稳态行为。研究发现,通过调节两个激发态的能级分裂宽度(即量子阱的耦合强度)、Fano型干涉和频率失谐,光学双稳态得到有效控制。还讨论了电子合作参数对光学双稳态的影响。同时,分析了基于不对称隧穿耦合双量子阱中间带跃迁的光学双稳态行为,这一量子阱是由探测光场和控制光场通过一个单向环型腔来驱使的。证明了可以通过调谐隧穿耦合的两电子能级间的能级分裂、控制场强度和频率失谐来控制光学双稳态,并讨论了电子合作参数对光学双稳态的影响。(5)运用一个射频或微波场驱动一对基态超精细跃迁,研究了四能级和五能级两种原子系统的自发辐射光谱特性。研究发现了一些有趣的现象,如谱线变窄、谱线增强、谱线抑制及荧光淬灭能够通过调节射频驱动场的相位、频率和强度来实现。在耦合和射频驱动场的缀饰态绘景中,该五能级原子系统相当于一个存在多通道自发辐射相干效应的真实原子系统。鉴于不存在(或者尚未发现)具有自发辐射相干效应的真实原子系统,文章等于提出了一种开展相关实验研究的可行性方案。(6)考虑到近偶极(NDD)相互作用下的密度依赖,从理论上研究了被单模探测激光驱动的三能级和四能级原子在光密介质中的非线性吸收―色散响应和布居动力学特性。通过数值计算预测了NDD效应对探测场的吸收―色散谱和布居动力学的影响。(7)通过引入一个附加信号场的扰动,在一个五能级原子系统中研究了在双暗态共振作用下的探测放大响应。研究发现,通过适当调节微波驱动场和信号激光场的强度,就能实现有或者没有布居反转的探测放大增强。根据量子干涉和缀饰态理论我们定量地解释了产生这些结果的物理机制。(8)研究了存在双暗态共振相互作用的五能级原子系统中双光子吸收的特征。结果发现,双光子吸收在两个不同频率处由于两相干耦合场而被完全禁止;原子系统存在抑制双光子吸收的双电磁诱导透明窗口。双光子透明窗口的位置及其宽度可以通过适当调节频率失谐量和两耦合场的强度来控制。另外,在双光子吸收谱中可以观察到一个增强窄中心谱线,这可能在精细光谱学中有所应用。从物理的观点来看,根据由三个不同双光子激发通道导致的量子干涉效应在修饰态绘景中对这些结果做了详细解释。总之,本论文的研究不仅有助于理解和掌握冷原子介质和半导体量子阱材料中相干非线性光学的新特性,而且对光信息的存储和提取、原子的相干操纵、全光开关、高精度非线性光谱学和量子信息学等高新技术的研发也大有裨益。更多还原

【Abstract】 In this thesis for the Doctorate, we have discussed mainly nonlinear optical features and its applications in quantum coherent media. More precisely speaking, we theoretically study optical nonlinear enhanced effects, ultralow optical solitons, high-efficiency mixing conversion, coherent control of optical bistability/multistability and spontaneous emission spectra as well as dynamics in both optically dilute and optically dense media.The work of our paper can be divided into the following eight parts:(1)We demonstrate the efficient generation of ultraslow bright and dark optical solitons in a lifetime-broadened three-level atomic medium by using only a low-intensity pulsed laser radiation.(2)The potential for nonlinear conversion between two laser pulses in a three-level V-type medium with assistance of an auxiliary microwave resonant radiation is studied. The results show that microwave driven field can lead to the parametric generation of a new laser pulse with high conversion efficiency when a weak pump laser pulse is applied.( 3 ) We analyze hybrid absorptive-dispersive optical bistability (OB) and multistability (OM) behavior in a generic N-type atomic system driven by a degenerate probe field and a coherent coupling field by means of a unidirectional ring cavity. We show that the OB can be controlled by adjusting the intensity and the detuning of the coupling field, and the OM can also be observed under the appropriate detuning. The influence of the atomic cooperation parameter on atomic OB behavior is also discussed.(4)We analyze hybrid absorptive-dispersive OB behavior via tunable Fano-type interference based on intersubband transitions in asymmetric double quantum wells (QWs) driven coherently by a probe laser field by means of a unidirectional ring cavity. We show that OB can be controlled efficiently by tuning the energy splitting of the two excited states (the coupling strength of the tunnelling), the Fano-type interference, and the frequency detuning. The influence of the electronic cooperation parameter on the OB behavior is also discussed.At the same time, we study OB behavior based on intersubband transitions in an asymmetric coupled-quantum well (CQW) driven coherently by a probe laser field and a control laser field by means of a unidirectional ring cavity. We demonstrate that OB can be controlled by tuning the energy splitting between two tunnel-coupled electronic levels, the intensity of the control field, and the frequency detuning of the probe and control fields. The influence of the electronic cooperation parameter on the OB behavior is also discussed.(5)We investigate the features of the spontaneous emission spectra in a coherently driven cold four-level and five-level atomic systems by means of a radio frequency (rf) or microwave field driving a hyperfine transition within the ground state. It is shown that a few interesting phenomena such as spectral-line narrowing, spectral-line enhancement, spectral-line suppression, and spontaneous emission quenching can be realized by modulating the phase, the frequency and intensity of the rf-driving field in our systems. In the dressed-state picture of the coupling and rf-driving fields, this five-level atomic system is equivalent in form to a real atomic system with multi-channel spontaneous emission coherence. With respect to no existence of the real atomic system with spontaneous emission coherence effect or not finding it, the paper amounts to proposing a feasible scheme of carrying out experimental investigation.(6)Taking the density-dependent near dipole-dipole (NDD) interaction into consideration, we investigate the response of nonlinear absorption and dispersion as well as population dynamics in optically dense media of three-level and four-level atoms driven by a single-mode probe laser. The influence of the NDD effects on the absorption-dispersion of the probe field and population dynamics is predicted via numerical calculations.(7)We investigate the response of the probe amplification in a five-level atomic system in the presence of interacting double-dark resonances disturbed by introducing an additional signal field. It is found that a large enhancement of the probe amplification with or without population inversion can be achieved by properly adjusting the strengths of the microwave driving field and the signal laser field. From viewpoint of physics, we qualitatively explain these results in terms of quantum interference and dressed states.(8)We investigate the features of two-photon absorption in a five-level atomic system with interacting dark resonances. It is found that two-photon absorption can be completely suppressed at two different frequencies due to the application of two coherent coupling fields and the atomic system exhibits double electromagnetically induced transparency windows against two-photon absorption. The position and width of the double two-photon transparency windows can be controlled via properly adjusting the frequency detuning and the intensities of the two coupling fields. In addition, one enhanced narrow central line can be observed in the two-photon absorption spectra, which may find applications in high precision spectroscopy. Form a physical point of view, we explicitly explain these results in terms of quantum interference induced by three different two-photon excitation channels in the dressed-state picture.In summary, these studies may be helpful not only to understand better the new characteristic of nonlinear optics in both the cold atomic media and semiconductor quantum-well material but also to the high techniques of optical information storage and retrieval, the coherent manipulation of atoms, all-optical switching and all-optical storage devices, high-precision spectroscopy as well as quantum information sciences.更多还原