Enhanced Optical Nonlinearity And Applications In Noble Metal Nanoparticle-microcavity Composite Systems

In recent years,more and more attention has been paid to the cavity optomechanics with the rapid development of micro-nano processing technology.Optical microcavity with small mode volume and high-quality factor can effectively couple with the mechanical oscillator through radiation pressure,resulting in a series of novel optical phenomena,such as the optomechanically-induced transparency,fast and slow light,group delay,optical frequency comb,etc.This has outstanding advantages in the fields of precision measurement,information storage,and photonic devices.This thesis primarily deals with two different hybrid optomechanical systems,whose nonlinear optical properties will be heavily analyzed and discussed,over a wide range of experimental parameters.Thanks to the intimate relation between the sideband generation efficiency and the size of the nanoparticle,we then theoretically design a self-reference highsensitivity optical sensor,using the hybrid optomechanical system as the core element,based on an efficient scheme we propose for improving the sensitivity.The specific contents of this thesis are as follows:1.The generation and control of optical second-order sideband are discussed in a hybrid cavity photomechanical system composed of semiconductor quantum dots(QDs),spherical metal nanoparticles(MNPs),and low-quality factor microcavity.The hybrid system is driven by a weak probe laser field and a strong control laser field.Different from the traditional linear description,we mainly use the perturbation method to solve the nonlinear Heisenberg Langevin equation to obtain the generation efficiency of the transmission spectrum and optical secondorder sideband output spectrum.It is shown that the hybrid of plasmon and cavity modes could induce the formation of the surface plasmon polaritons,resulting in a controllable interaction that can be enhanced into a strong coupling regime even if the cavity–QD interaction is initially in the weak-coupling regime.As a result,enhanced optical second-sideband generation and the splitting of the transmission spectra can be observed.In addition,the theoretical results also show that the size of metal nanoparticle has a significant impact on the generation efficiency of the second-order sideband,which can be used to design an accurate self-reference detection scheme to extract the size information of metal nanoparticles.2.Based on the nonlinear optical response of the system,we theoretically discuss the sum sidebands induced by radiation pressure and their frequency characteristics in the hybrid cavity optomechanical system that is composed of noble metal nanoparticles.Under the influence of the double detection fields,a new frequency component,namely the sum sideband,will be generated in the output light due to the nonlinearity of optomechanical coupling.Through theoretical discussion,the matching conditions of the upper sum sideband and lower sum sideband are given respectively.And it is found that under the influence of the surface plasmon polaritons,the generation efficiency of the sum sideband is closely related to the size of nanoparticle.According to this feature,a high-sensitivity nanoparticle size detection device based on a hybrid cavity optomechanical system is put forward in theory,and the detection sensitivity is effectively improved by controlling the dissipation of the mechanical oscillator.This provides a new idea for high-precision measurement and on-chip preparation.In a word,the contents studied and discussed in this thesis are of great significance to further understand the nonlinear optical characteristics of hybrid cavity optomechanical systems.And the surface plasmon polaritons of noble metal nanomaterial can effectively improve the nonlinear response,which has a unique value in the fields of precision measurement,information storage,and so on.