对三能级电磁感应透明原子系统的密度矩阵方程进行解算，获得该系统九个密度矩阵元的色散行为,同时研究探针光与控制光所对应的原子气体介电系数的色散曲线和一般相干操控特性。本文将控制光与探针光同等看待，即不同于以往着重于探针光特性、将控制光仅当作调控电磁感应透明介质光学特性的外部条件看待、从而没有研究控制光本身如何受探针光的影响。本文研究探针光与控制光之间的彼此影响(即彼此受对方操控的行为)。电磁感应透明介质内由光来控制光的量子相干行为可以作为新型光子学器件设计的基本原理。 The equation of motion of the density matrix of a three-level EIT (electromagnetically induced transparency) atomic system is solved and the behavior of dispersion of the nine density matrix elements is presented. The general optical response of the electric permittivity corresponding to both the probe and the control fields is addressed based on the numerical results of the equation of motion of the density matrix. The probe and the control fields are treated in the same way, in which the influence of the probe field on the control field (and vice versa) is considered. The optical be- havior of controlling light with light can be a fundamental mechanism for new photonic and quantum optical device design.
对三能级电磁感应透明原子系统的密度矩阵方程进行解算，获得该系统九个密度矩阵元的色散行为,同时研究探针光与控制光所对应的原子气体介电系数的色散曲线和一般相干操控特性。本文将控制光与探针光同等看待，即不同于以往着重于探针光特性、将控制光仅当作调控电磁感应透明介质光学特性的外部条件看待、从而没有研究控制光本身如何受探针光的影响。本文研究探针光与控制光之间的彼此影响(即彼此受对方操控的行为)。电磁感应透明介质内由光来控制光的量子相干行为可以作为新型光子学器件设计的基本原理。 The equation of motion of the density matrix of a three-level EIT (electromagnetically induced transparency) atomic system is solved and the behavior of dispersion of the nine density matrix elements is presented. The general optical response of the electric permittivity corresponding to both the probe and the control fields is addressed based on the numerical results of the equation of motion of the density matrix. The probe and the control fields are treated in the same way, in which the influence of the probe field on the control field (and vice versa) is considered. The optical be- havior of controlling light with light can be a fundamental mechanism for new photonic and quantum optical device design.
研究了在不同温度下三能级相干原子气体的光学特性(介电系数和群速)色散行为。求解三能级原子系统完备密度矩阵方程，得到所有密度矩阵元的色散行为，然后考虑多普勒频移修正和原子气体饱和蒸汽压(饱和密度)随着温度的变化关系，进行数值求解，给出了探针光群速的色散行为及与原子蒸汽温度的函数依赖关系图示。本文所研究的不同温度下三能级相干原子气体的光学特性可以作为某些温控光子学器件(如光子开关、光逻辑门、光子晶体管)的基本物理原理。 The dependence of dispersion characteristics of electric permittivity and group velocity on the temperature in a three-level quantum coherent atomic vapor is considered based on the numerical solution of the density matrix equation of the three-level atomic system. The behavior of dispersion of all the density matrix elements has been obtained, and both the Doppler frequency shift and the saturation density that depend upon the temperature of the saturated atomic vapor have been taken into account. The presented optical response of the quantum coherent vapor can be utilized as a fundamental mechanism for some temperature-controlled photonic devices such as optical switches, photonic logic gates and optical transistors.
Summary form only given. Electromagnetically induced transparency (EIT) refers to a phenomenon, whereby the optically resonant transition is rendered nearly transparent by applying a strong coupling laser field. The mechanism of EIT is usually explained in terms of quantum coherence or quantum interference. This EIT has attracted increasing interest because absorption associated with nonlinear optical processes can be removed. In the typical three-level /spl lambda/-system, which includes the ground state and the metastable state, when the atomic population is prepared in the superposition of the states by the coupling fields, the optical response of the media to the probe field is significantly modified. Since this is a coherent control of an electric field by another field via the atomic coherence, several schemes to control light coherently have been suggested. We propose an optical coherent control scheme of the polarization of optical pulses using the EIT quantum coherence, and numerically study its applicability to fast optical switching.
A periodic layered medium, with unit cells consisting of a dielectric and an electromagnetically-induced transparency (EIT)-based atomic vapor, is designed for light propagation manipulation.Considering that a destructive quantum interference relevant to a two-photon resonance emerges in EIT-based atoms interacting with both control and probe fields, an EIT-based periodic layered medium exhibits a flexible frequency-sensitive optical response, where a very small variation in the probe frequency can lead to a drastic variation in reflectance and transmittance.The present EIT-based periodic layered structure can result in controllable optical processes that depend sensitively on the external control field.The tunable and sensitive optical response induced by the quantum interference of a multi-level atomic system can be applied in the fabrication of new photonic and quantum optical devices.This material will also open a good perspective for the application of such designs in several new fields, including photonic microcircuits or integrated optical circuits.
The author of this thesis concentrates his attention on quantum optical properties of some artificial electromagnetic media, such as quantum coherent atomic vapors (various multilevel electromagnetically induced transparency vapors) and negative refractive index materials, and suggests some possible ways to manipulate wave propagations inside the artificial electromagnetic materials based on quantum coherence and quantum vacuum effects. In Chapters 1 and 2, the author reviews the previous papers on quantum coherence as well as the relevant work such as electromagnetically induced transparency (EIT), atomic population trapping and their various applications. The basic concepts of quantum coherence (atomic phase coherence, quantum interferences within atomic energy levels) and quantum vacuum are introduced, and the theoretical formulations for treating wave propagations in quantum coherent media are presented. In Chapter 3, the author considers three topics on the manipulation of light propagations via quantum coherence and quantum interferences: i) the evolutional optical behaviors (turn-on dynamics) of a four-level N-configuration atomic system is studied and the tunable optical behavior that depends on the intensity ratio of the signal field to the control field is considered. Some typical photonic logic gates (e.g. NOT and NOR gates) are designed based on the tunable four-level optical responses of the N-configuration atomic system; ii) the destructive and constructive quantum interferences between two control transitions (driven by the control fields) in a tripod-type four-level system is suggested. The double-control quantum interferences can be utilized to realize some photonic devices such as the logic-gate devices, e.g., NOT, OR, NOR and EXNOR gates; iii) some new quantum coherent schemes (using EIT and dressed-state mixed-parity transitions) for realizing negative refractive indices are proposed. The most remarkable characteristic (and advantage) of the present scenarios is such that the isotropic left-handed media (with microscopic structure units at the atomic level) in the optical frequency band can be achieved. Quantum vacuum (the ground state of quantized fields) can exhibit many interesting effects. In Chapter 4, we investigate two quantum-vacuum effects in artificial materials: i) the anisotropic distribution of quantum-vacuum momentum density in a moving electromagnetic medium; ii) the angular momentum transfer between quantum vacuum and anisotropic medium. Such quantum-vacuum macroscopic mechanical effects could be detected by current technology, e.g., the so-called fiber optical sensor that can measure motion with nanoscale sensitivity. We expect that these vacuum effects could be utilized to develop sensitive sensor techniques or to design new quantum optical and photonic devices.In Chapter 5, the author suggests some interesting effects due to the combination of quantum coherence and quantum vacuum, i.e., the quantum coherent effects, in which the quantum-vacuum fluctuation field is involved. Two topics are addressed: i) spontaneous emission inhibition due to quantum interference in a three-level system; ii) quantum light-induced guiding potentials for coherent manipulation of atomic matter waves (containing multilevel atoms). These quantum guiding potentials could be utilized to cool and trap atoms, and may be used for the development of new techniques of atom fibers and atom chips, where the coherent manipulation of atomic matter waves is needed.In Chapter 6, we conclude this thesis with some remarks, briefly discuss new work that deserves further consideration in the future, and present a guide to the previously published papers by us.
Using density matrix eqution, the absorption and dispersion properties of a A-type four-level system driven by coherent fields are investigated. The result obtained by means of numerical method indicates that by adjusting the intensity of Rabi frequencies of the coherent field in the steady state, three, double or single electromagnetically induced transparency (EIT) can appear explicitly in this system. And the explanations of these phenomena are given by using the dressed states. In the three EIT, the location of transparent windows can be manipulated by controlling the detuning of the driving field. What's more, it is also found that the medium shows a large refractive index at each transparency window, and the group velocity of the probe laser can be enhanced.
Electromagnetically induced transparency (EIT) resonance is obtained in a well-studied lambda three level system where an optical coupling field and a probing field interact with two optical transitions. However, both electromagnetically induced absorption (EIA) and EIT can be obtained in a modified quasi-lambda four level system consisting of an optical-radio two-photon coupling field and a probing field. By solving the density matrix equation of motion, a physical account of EIA and EIT is given in terms of a dressed state picture. It can be seen that the optical coupling field in this quasi-lambda four level system has a crucial effect on the forming of EIA and EIT. An EIA is observed under a resonant optical coupling and it evolves into an EIT when there is a detuning. Furthermore, the width of EIA or EIT increases as the optical coupling Rabi frequency increases.