Study On The Strong Coupling Phenomenon In Open Quantum Systems And The Manipulation Of Classical Waves Via Artificial Microstructures

With the emergence and constant improvement of the theory of quantum optics since the middle of 20th century,the light-matter interactions are now comprehensively depicted by modern quantum theory.And it is still being further investigated.The strong coupling between quantum emitter(QE)and the surface plasmonic(SP)modes supported by nanometric cavities has been a hot topic recently.At the beginning of this century,the theory of Transformation Optics(TO)is proposed and extensively developed by exploiting the fruitful exsiting results in complex analysis and general relativity.The theory opens a new way of devising artificial structures to control classical wave motion.Meanwhile,with the rapid development of new technologies in experiment,especially the nanometric fabrication and the 3D printing techniques,the experimental investigation in the above-mentioned fields has also been fruitful.In this thesis,we are going to exhibit the research results obtained during my PhD years,which are based on the achievements made by numerous researchers in the related fields.The thesis is divided into following sections:In Chapter I,a brief introduction is given on the research status of Transformation Optics(TO),Surface Plasmon Polariton(SPP),and the strong coupling(SC)phenomenon of quantum emitters(QEs)in plasmonic nanocavites.In Chapter II,the theories and methods untilized thoroughout the thesis are reviewed,including the theory of Transformation Optics,the canonical quantization of radiative electromagnetic(EM)fields,quantum description of the interaction between QEs and EM fields,the introduction of the spectral density and the Wigner-Weiskopf problem,and the effective medium theory of phononic crystals under the long-wavelength approximation.In Chapter III,the plasmon-exciton strong coupling in nanocavities is studied.Under the theoretical framework of Transformation Optics,the sprectral density of the QE-dimer system is obtained both numerically and quasi-annalytically.The population dynamics is also studies which gives sufficient support for exploring the physical mechanism of SC of single QEs with SPs in a metallic dimer cavity.With the help of the Lorentzian-mode decomposition of the spectral density,two groups of hybridized SP modes with even and odd spatial symmetries and their corresponding excitation conditions are discovered.Finally the results of the recently published experiment on single-molecule strong coupling at room temperature in plasmonic nanocavities is retrieved with the developed theory with a relatively high accuracy.In Chapter Ⅳ,the classical wave analogue of celestial mechanics is studied.The conformal transformation is utilized to mimick the light propagation near celestial black holes.This analogue provides a possible scheme of investigating celestial phenomena under the conditions of the common optics labortaries.In Chapter Ⅴ,the asymmetric acoustic propagation in a waveguide is studied.A two-dimentional gradient index configuration is proposed,which renders completely different physical mechanism compared with the previously devised structures.An implementation based on phononic crystals is designed,which shows very good agreement with the parameter-based prototype in numerical simulations.This configuration has its unique potential applications in fields like ultrasound therapy.Finally,in Chapter Ⅵ,the conclusions and the innovation points are summarized and the outlook of future development of the current works is briefly described.The main innovations of this paper are as follows:1.For the first time,the theory of TO is used to solve the QE-SP strong coupling problem in quantum optics.Numerical and quasi-analytic results reveal the physical mechanism of QE-SP strong coupling in the dimer cavity.Based on the acquired results,we analyzed the recently published experiment which realized the single QE-SP strong coupling at room temperature.The analytical results exhibit a good match with the experimental data;2.For the first time in acoustics we proposed an omnidirectional sound absorber that mimics celestial mechanics with acoustic beams,and put forward the possible realization of the structure;3 we achieved the asymmetric transmission of sound waves in a straight acoustic waveguide.