Tunable Superluminal And Subluminal Light Propagations In The Dispersive Devices

Controlling of the light propagation is a hot research topic in the recent years.The ability to control the group velocity of optical wave packets,or light pulses,is very attractive both for the understanding of the fundamental physics underlying the light-matter interaction,and the potential applications in optical signal processings.Based on these,this thesis investigates the optical propagation characteristics in different dispersive materials,and discusses the influence of the dielectric material and the structure parameters on the optical propagation characteristics.The chapters are organized as follows:Chapter 1 introduces the research background of light pulse propagation in optical system The physical mechanisms and research status of slow light and fast light phenomena are demonstrated respectively,and the calculation method used in this thesi,s is also exhabitedChapter 2 introduces the counterintuitive dispersion effect in the gain slab system.This effect is related to the locations of the singular points for the response function in the complex frequency domain.Traditionally,the singularity is always in the lower-half complex frequency domain,when it moves to the upper-half complex frequency domain,the peak in the spectrum corresponds to the anomalous dispersion,this relation is completely different from the traditional Kramers-Kronig relationship.This effect leads to two unique features:a broadband abnormal dispersion region and an observable Hartman effect.The counterintuitive dispersion effect can be explained in terms of interference and boundary effects.Finally,two experiments are proposed for the potential experi-mental verification.chapter 3 describes the counterintuitive dispersion effect when a surface plasmon resonance is excited.This effect associates with movements of the poles and zeros of the transfer functions.The zeros and/or poles in the reflection and transmission functions may move into the upper-half complex-frequency plane(CFP),and these locations of the zeros and poles determine the dispersion properties of the whole structures(i.e.,the frequency-dependent change of both re flected and transmitted phases).For a realistic metal substrate in an Otto structure,there are the optimal thick-ness and incident angle,which correspond to the transitions of the zeros in the reflection function from the upper-half to lower-half CFP,the dispersion relations and the group delays of the reflection light pul,se are totally different near the optimal points.These properties may be helpful to manipulate light propagation in optical devices.Chapter 4 describes the propagation of a light pulse reflection from the layer system with a graphene layer.A tunable transition between positive and negative group delays of optical pulse reflection in such a layered system controlled by the properties of the graphene layer has been demonstrated,and two mechanisms to control the propagation properties of the light pulse reflected from such systems have been revealed.It is demonstrated that the reflected group delays are tunable from positive to negative values in both mechanisms of resonances and the excitations of surface plasmon resonances,which are also adjusted by tuning the Fermi energy and temperature of the graphene layer.These results are useful for design of graphene-based optical devices.Chapter 5 investigates the band structures of one-dimensional photonic crystals(1DPCs)composed of Dirac materials and ordinary dielectric media.It is found that there exist an omnidirectional passing band and a kind of special band,which result from the interaction of the evanescent and propagating wave,s.Due to the interface effect and strong dispersion,the electromagnetic fields inside the special bands are strongly enhanced.It is also shown that the properties of these bands are invariant upon the lattice constant but sensitive to the resonant conditions.Chapter 6 summarizes the main work of this thesis,and gives the innovation of the work Moreover,the direction of the future work has been demonstrated.