Research On Light Confinement And Emission In WGM Microcavity

Due to their wide applications in both fundamental studies and practicalapplications such as optical interconnect, optical communication, dielectricmicrocavities have attracted intense research attention in past decades. In conventionalwhispering gallery based microcavities, the light is trapped by total internal reflectionalong the cavity boundary for a long time. Such localization gives extremely high Qfactors, which are essential for ultralow thresholds, ultrahigh sensitivity et alIn order to improve the directionality, asymmetrical resonant cavities (ARC) havebeen proposed and soon after experimentally fabricated in1997. The breaking ofrotational symmetry introduces many new characteristics, e.g.,the coexistence ofordered states and disordered (chaotic) modes. Classically, the ray dynamics haveshown that the refraction of chaotic motions along the unstable manifolds plays key rolein the directional emission of ARC, although a serious Q spoiling is usually associated;the regular states such as islands can trap light infinitely but still suffer with thedirectional outputs. In wave optics, the barrier between the regular and chaotic statescan be penetrated through a recent discovered quantum phenomenon, dynamicaltunneling, which is essential to combine the high Q factor and directional outputs.In this thesis, we will show our investigations on the dynamical tunneling effectbetween the regular state and chaotic sea. We demonstrate that not only the well knowdynamical tunneling but also the nontrivial effect-coherent destruction of dynamicaltunneling can also happens in chaotic cavities. Our findings give a new rout to controlthe interaction between regular and chaotic states, which shall dramatically enhance thefundamental studies on quantum chaos and practical applications in beam steeringsimultaneously.This thesis focuses on the following aspects:First, we establish a ray tracing model. Taking account the incident angle andAzimuthal angle as momentum and positon, we have projected the real spacetrajectories to phase space, the so-called Poincare surface of section.The phase spacestructures and the corresponding survival probability in open boundary give the simplepredictions and understandings of wave phenomena in cavities.Second,by applying a finite element method (FEM) based commercial software,we have numerically solved the Helmholtz equations and achieved the resonanctrequencies, Q factors, mode patterns, and corresponding far field patterns (FFPs) of thedesigned ARCs. We have observed very nice consistence between the results calculatedwith ray dynamics and wave equations.Finally, we introduce the quantum effect, the avoided resonance crossing, into the ARCs and studies their Q factors and FFPs. We find that, the external coupling betweenresonances localized within different regions of phase space can dramatically changethe dynamical tunneling rate. Around the crossing point, a reversed process, thecoherent destruction of dynamical tunneling, can also be obtained. The consequentresult is the switching between bi-directional and four directional outputs, which areformed by the conventional direct tunneling. Moreover, we have also presented apossible way to control the coherent destruction of dynamical tunneling in realexperiment.