【作者】 陈玺；

【导师】 李春芳；

【作者基本信息】 上海大学 ， 无线电物理， 2007， 博士

【摘要】 随着科学技术的不断进步和信息社会的发展，集成光学，大规模集成电子线路和量子电子器件等信息技术已逐步接近和达到微纳尺度，对此领域的研究是21世纪高新技术发展所急需的先导和支撑．本论文围绕着微结构中波的动力学及共振现象这一主题开展研究．作者取得的主要研究成果是：(1)研究了光学微结构中有限光束的反常侧向位移及其机制．首先，研究了有限光束穿过薄介质板时透射光束存在侧向位移、角偏转、束腰宽度的修正以及焦点的纵向移动四种非几何光学效应，给出了该侧向位移反向时入射角及介质板的厚度所需满足的必要条件，报道了利用微波技术首次在实验上观测到穿过薄介质板时波束的反向位移．其次，研究发现了有限光束穿过左手介质板时共振增强的侧向位移，可以为负，也可以为正．这个结果说明，薄介质板结构中的负侧向位移与负折射率材料无关，是介质板边界效应相互作用的结果．最后，我们利用多个有限光束之间的干涉效应揭示了薄介质板结构中反常侧向位移的物理机制。(2)研究了二维量子微结构中电子束的空间位移及其调制。研究发现电子束穿过半导体量子势垒的空间位移与电子波的Snell定律预言的结果不同，并且当电子束的入射角小于且接近临界角时透射电子束的空间位移具有共振增强效应。其次，发现在半导体量子势阱结构中透射或反射电子束的空间位移可以为正也可以为负，并且给出了电子束位移为负的必要条件。更重要的是，首次发现了在磁电势垒结构中电子束的正、负位移可以通过外加电场或磁场进行调制．这些新奇现象将为新型量子电子器件提供新的思路。(3)研究了量子结构中粒子的反常群时延及其物理机制。人们已经在理论和实验上证明了量子势阱中粒子的负群时延。在此基础上，系统地研究了单个非对称量子势垒中反射和透射时延。研究发现，在消逝场和行波场的情况下，反射和透射时延与势垒高度以及势垒外两边势能的相对高度有关，且可正或可负。在消逝场的情况下，即当粒子的入射能量比势垒高度低时，在非透明势垒极限下反射和透射时延与势垒厚度无关，表现出超光速性。在行波场的情况下，即当粒子的入射能量大于势垒高度时，反射与透射时延是势垒厚度的周期函数，具有共振增强效应。最后，从多个波包干涉的角度解释了量子势阱结构中粒子的负群时延，并且进一步揭示了量子势垒结构中Hartman效应的本质。(4)研究了相对论性粒子在量子结构中的渡越时间。首先，主要讨论了相对论性粒子穿越量子势阱群时延的性质。研究表明，相对论性粒子穿越势阱的时延与非相对论的情况类似具有超光速性，甚至可以为负，并且提出了群时延为负的必要条件。进一步分析发现负群时延与其在共振点处反常依赖于势阱宽度有关。数值比较说明了在相对论量子理论中群时延大于在非相对论量子理论中相应的群时延。此外，进一步推广了在非相对论量子理论中一种不具有超光速的渡越时间——能量转移时间，分别讨论了消逝场和行波场两种情况下相对论性粒子穿过势垒时该渡越时问的亚光速性。研究表明，在消逝场情况下，能量转移时间的特性与非相对论的情况类似，不具有超光速性。同样，在行波场情况下，能量转移时间也不存在超光速的问题。更多还原

【Abstract】 With the progress of science & technology and the development of information society, information technology such as integrated optics, large-scaled integrated circuits and quantum electronic devices has approached and even reached nanometre scale. Therefore, the research in this field is the forunner and basis for the high technology development in the 21st century. In this Ph. D. dissertation, the investigations of the wave dynamics and its resonance phenomena in the microstructures are presented. The main results given by the author are as follows:(i) The anomalous lateral displacement and its mechanism in the optics microstructures are investigated. Firstly, it is reported that the finite-sized light beam transmitted through a thin dielectric slab experiences four non-geometric effects, such as lateral displacement, angular deflection, modification of waist width, and longitudinal focal shift. Necessary conditions are advanced for the lateral displacement to be backward. The experimental observations of the backward displacement in the microwave region are reported for the first time. Secondly, I have found that the resonance-enhanced lateral displacement of the light beam transmitted through a left-handed slab can also be negative as well as positive. These show that the negative lateral displacement of the finite-sized light beam transmitted through a thin dielectric slab is the result of the interaction of the boundary effects of the slab, and have nothing to do with the negative refractive index itself. Finally, we have investigated the origin of the anomalous displacements in a thin dielectric slab by the interference between the multiple finite-sized light beam.(ii) The lateral displacements of the electron beam and their modulation in the two-dimensional quantum microstructures are investigated. It is found that the displacement of the electron beams transmitting through a two-dimensional semiconductor barrier is quite different from the prediction from Snell’s law for electron waves. It is shown that the displacement can be greatly enhanced by transmission resonance when the incidence angle is less than but close to the critical angle for total reflection. In addition, the lateral displacement of the transmitted electron beam through a semiconductor quantum well can be negative as well as positive. The necessary condition is obtained for the displacement to be negative. More importantly, the positive and negative displacements of the electron beam in transmission through a two-dimensional electron gas can be modulated by a ferromagnetic (FM) stripe under an applied voltage. These phenomena may lead to novel applications in quantum electronic devices.(iii) The anomalous group delay in the quantum structures and its mechanism are investigated. The theoretical and experimental researches have demonstrated that the group delay for quantum particles traveling through a potential well can be negative. Accordingly, the reflection and transmission group delay times are systematically investigated in an asymmetric single quantum barrier. It is found that the reflection times in both evanescent and propagating cases can be negative as well as positive, depending on the relative height of the potential energies on the two sides of the barrier. In evanescent case where the energy of incident particles is less than the height of the barrier, the reflection and transmission group delay times in the opaque limit are both independent of the barrier’s thickness. In the propagating case where the energy of incident particles is larger than the height of the barrier, the group delay times depend periodically on the barrier’s thickness, thus can be greatly enhanced by the transmission resonance. Finally, the physical mechanism of superluminal and even negative group delay in quantum well structure and the nature of Hartman effect in quantum barrier structure are investigated from the viewpoint of interference between multiple finite wave packets, due to the multiple reflections.(iv) The traversal times for Dirac particles through the quantum microstruc-tures are investigated. Firstly, the properties of group delay for Dirac particles traveling through a quantum potential well are investigated. A necessary condition is put forward for the group delay to be negative. It is shown that this negative group delay is closely related to its anomalous dependence on the width of the potential well around the resonance points. Furthermore, a traversal time that has no problem of superluminality for particles to tunnel through potential barriers in the non-relativistic quantum theory is generalized to Dirac’s relativistic quantum theory. Both evanescent and propagating cases are considered. It is shown that the traversal time in the evanescent case has much the same properties as in the non-relativistic quantum theory and thus has no problem of superluminality. It also gets rid of the problem of superluminality in the propagating case. Comparisons with the dwell time, the group delay, and the velocity of monochromatic front are also made.更多还原