Study Of Optical Properties Of New Artificial Electromagnetic Media

The electromagnetically induced transparency (EIT) media and negative index media (NIM), which are two of the most intriguing artificial electromagnetic materials in optics and materials science, have captured extensive attention of many researchers in various fields. The author of this thesis concentrated his attention primarily on the novel optical properties of these two artificial media. There is a connection between EIT media and NI media: specifically, under certain conditions, the EIT media can be changed into the NI media in the certain probe frequency ranges. In the present thesis we considered this subject in more details in Chapter III and IV.The content of every chapter, including the background, results and significance, is listed as follows:In Chapter I we present the literature overview and the introduction to EIT. We first review the brief history of research of quantum coherent effects as well as of EIT effect since 1970s. The main features, potential and practical applications of EIT are discussed also in both the brief history and the sections that follow. The electric polarization and magnetization due to atomic level transition, the transition-dipole matrix elements (and hence the electric permittivity and magnetic permeability) in atomic systems are derived. The local-field correction made to the electric and magnetic polarizabilities of multilevel atomic vapor systems is finally presented. In addition, the fundamental properties of double-negative (left-handed) materials are presented. Double-negative materials, which have simultaneously negative permittivity and negative permeability, are one kind of negative index media. It can be readily verified that the double-negative media exhibit a number of peculiar electromagnetic and optical properties, including the reversals of both Doppler shift and Cherenkov radiation, anomalous refraction, amplification of evanescent wave, modified spontaneous emission rates as well as unusual photon tunneling effect. All the theories, concepts, approaches and formalism mentioned in this chapter will be applied to the subjects and topics in the chapters that follow.In Chapters II we present some preliminary topics related to the quantum coherent effects. We consider some problems in connection with electromagnetic induced transparency, including the stabilization of EIT phenomenon, three-level dressed states, elimination of vacuum spontaneous emission in a three-level system as well as periodic EIT medium. To the best of our knowledge, most of these problems have so far never been considered in the literature. We think these topics may have relevance to the fundamental properties arising in EIT. This may enable us to better understand phase coherence and quantum interference in quantum optics.In Chapters III and IV we consider possibility of realizing negative permittivity and negative permeability in a three-level EIT vapor medium. Generally speaking, the magnetic-dipole transition does not need to be considered in the treatment for the wave propagation in a conventional electromagnetic material. However, this may be not true in some certain EIT systems, where the coupling level pair (coupled to thecontrol laser beam) is nearly degenerate. The population in the lower coupling level is much greater than that in the excited level inside a three-level EIT medium where the intensity of coupling laser is much stronger than that of the probe light. In other words, the stronger coupling laser enhances the probability amplitude of the lower coupling level via quantum coherence and interference. Thus, the order of magnitude of the density matrix element associated with probe magnetic transition may be larger than that of the density matrix element associated with the probe electric transition. The magnetic transition in the system under consideration thus deserves investigation. Further analysis shows that a dense EIT gas medium may exhibit simultaneously negative permittivity and permeability, and will therefore become an ideal candidate for realizing isotropic left-handed media at atomic level and in an optical frequency range.In Chapter V the local field correction (LFC) is made to both three- and four-level systems. In the previous studies in the literature, local field effects (and the Clausius-Mossotti relation) in the electric response of atomic media were not taken into account. However, there may be two cases which need consideration of local field effects: in the case of dense gas and the case of off resonance. The polarizabilities and susceptibilities of both three- and four-level systems are numerically plotted in order to present a comparison between two cases with and without LFC. Based on this we obtain the value of critical density that can make difference between dilute and dense vapors.In Chapter VI the electromagnetic field quantization is taken into account for the chiral media. Dung, Buhmann et al. recently investigated the electromagnetic-field quantization and then considered the spontaneous emission and Einstein's absorption/emission coefficients in negative refractive index materials. Besides Dung, Buhmann et a/.'s work, Milonni and Maclay gave another version of field quantization in isotropic left-handed media. These studies clarified some puzzles arising from the negative value of the refractive index. More recently, Tretyakov and Pendry et al. demonstrated that the backward waves can propagate in chiral materials with positive permittivity and permeability parameters. Therefore, we think it is necessary to consider the field quantization in chiral media. We obtain the quantized electromagnetic energy density and Poynting vector of propagating waves inside chiral media.In Chapter VII a scheme of utilizing so-called gyrotropic chiral media to realize negative refraction is suggested, which generalizes the recent studies of Tretyakov and Pendry et al, who demonstrated that the chiral nihility (and hence negative refraction) can be achieved at or near the resonant frequency of permittivity of chiral media. But the nihility does not arise in the case of far off resonance. In the present chapter, we consider the backward wave propagation in a generalized material (gyrotropic chiral medium). We think the gyrotropic chiral media may have an advantage over the chiral media to fabricate negatively refracting materials: specifically, the gyrotropic nihility may be achieved in the non-resonance frequency band, and the negative refraction may therefore be conveniently realized experimentally.As the EIT-based realization of negative refractive index was presented in Chapters III and IV, we take into account the optical properties of negative refractive index materials (including artificial metamaterials) in chapters that follow. From Chapter VIII to X, some physically interesting properties and effects (including the quantum effects) of wave propagation in biaxially anisotropic left-handed materials are investigated: (i) the left-right coupling of circularly polarized light arises in the biaxially gyrotropic left-handed material due to the negative indices in permittivity and permeability tensors of gyrotropic media;(ii) for the light propagating inside certain anisotropic left-handed media a new geometric phase that is independent of the cone angles is suggested;(iii) the extra phases of electromagnetic wave resulting from the instantaneous helicity inversion at the interfaces between left- and right-handed (LRH) media is studied in detail by using the Lewis-Riesenfeld invariant theory. Some interesting applications (e.g., controllable position-dependent frequency shift, detection of quantum-vacuum geometric phases and helicity reversals at the LRH interfaces etc.) of above effects and phenomena in left-handed media are briefly discussed.In Chapter XI we consider some interdisciplinary topics: the coherent control of quantized light fields and atomic matter waves in the coiled fibers. For example, a phenomenological description of time evolution of atomic matter waves inside a spiral shaped atomic-wave guide is presented;the nonadiabatic conditional geometric phase shift in a coiled fiber system is suggested.In Chapter XII we conclude with some remarks, and suggest some topics that deserve further consideration in the future.