Optical Properties And Coherent Control Of Weak Interactions Between Localized Surface Plasmons And Excitons

The interaction between light and matter has always been a hot research topic.Due to the mismatch in scale between atoms and optical fields,the interaction between light and matter in free space is very weak.The coupling between localized cavity modes and quantum systems has been an important topic in quantum information science and technology research.Related researchs are not only of great significance for the development of quantum theory,but also lay the foundation for exploring advanced quantum applications.In cavity quantum electrodynamics,the local photon density inside the cavity can be altered by optimizing the quality factor of the cavity,reducing the cavity mode volume,and the other means,which in turn enhances the coupling between the localized cavity field and the confined emitter.Among these means,the high-quality factor dielectric microcavity provides an effective approach for achieving strong coupling between light and matter.However,limited by the optical diffraction limit,the size of the dielectric microcavity restricts its application in the micro-nano scale,which is not conducive to the development of miniaturized devices.With the continuous progress of nanofabrication technology,researchers are gradually turning their attention to the study of surface plasmon systems in order to further increase the local photon density and reduce the system size to subwavelength scale.Metal particles with nanometer size can support localized surface plasmons(LSPs),which can localize the optical field in an area far below the diffraction limit and achieve significant field enhancement in the near-field region.Metal nanoparticles(MNPs),with their ability to confine light at subwavelength scales and enhance fields in the near-field region,can be regarded as plasmonic cavities,making them an ideal system for studying the fundamental physics of light-matter interactions in the nanoworld.Semiconductor quantum dots(QDs)possess significant advantages in the fundamental research of light-matter interactions owing to their broad excitation wavelength range,high fluorescence intensity,long lifetime,and strong oscillator strength.Excitons are quasiparticles that arise from the Coulomb interaction between electrons in the valence band and holes in the conduction band in the QD.The advancement of modern nanotechnology has facilitated the investigation of optical properties and coherent control of weak interactions between LSPs and excitons,which has garnered significant interest in the realm of quantum science.This system holds immense potential for various applications,including surfaceenhanced Raman scattering,surface-enhanced fluorescence,biosensing,single-photon sources,and quantum information.This article is based on the weakly coupled system of LSPs and excitons and investigates the following topics:1.The magnetically induced optical transparency effect and the coherent control of scattering spectra in the LSPs-excitons system are investigated.MNP provides LSPs mode,which interact with excitons in semiconductor QD,while the QD is subjected to a magnetic field generated along its growth direction.By using the full quantized physical model and experimental parameters,the scattering spectra of the composite system are studied in detail by means of the exactly numerical solution of the master equation and the approximately analytical solution of the perturbation method,and the effects of different parameters on the optical properties of the system are discussed.The phenomenon of magnetically induced optical transparency in the system is discovered,and its underlying mechanism is elucidated.The analytical and numerical results show that the scattering spectra can be effectively regulated by the external magnetic field under the weakly coupled LSPs-excitons condition,and the scattering spectra of the composite system can present a nearly absorption-free scattering window.Physically,this phenomenon is due to the quantum interference between the paths of emitted photons from excitonic states,which are caused by the Zeeman splitting induced by an external magnetic field.In addition,in the presence of the magnetic field,the system displays sharp double Fano resonance line shapes,and control over the spectral linewidth and peak can be achieved by designing the radius of the nanoparticle or the distance between the nanoparticle and QD.This scheme provides new degrees of freedom for effectively controlling spectra and obtaining desired spectral line shapes,and has certain application value in the development of sensitive on-chip quantum devices.2.The fluorescence spectra and their coherent control in the LSPs-excitons system under squeezed vacuum are investigated,revealing the Fano resonance fluorescence characteristics of the system.The optical properties of the artificially hybrid molecule composed of an MNP and a semiconductor QD driven by an external laser field are theoretically investigated using the fully quantized method under experimental parameters,with a focus on the influence of the squeezed vacuum field.The results of the study demonstrate that,under weak coupling conditions,the squeezed vacuum field can be utilized to design and control the peak amplitude,width,and shape of resonant fluorescence spectra.The rich spectral response reveals some intriguing phenomena,including Fano resonance fluorescence,fluorescence quenching,fluorescence narrowing,and fluorescence enhancement.The distinctive spectral response of these solid-state nanostructures holds potential for applications in developing quantum plasma platforms and highly sensitive onchip devices such as optical switches and sensors.3.The study investigate the photon correlation and their coherent control in a LSPsexcitons-microcavity composite system.By placing a nanoparticle and a QD in an optical microcavity,coherent tripartite coupling can be established among the nanoparticle,QD,and optical microcavity,resulting in the construction of a LSPs-excitons-microcavity composite system.Using two methods,exactly numerical solution of the master equation and approximately analytical solution of the Schr?dinger equation,we investigate the quantum correlation of photons in the tripartite composite structure,analyze the generation and principles of non-classical effects,and explore methods for manipulating photon statistics.The research findings indicate that the introduction of nanoparticles results in quantum interference between different two-photon excitation pathways in the hybrid system,which enables the system to exhibit nonclassical quantum effects such as photon blockade and photon bunching,even under the bad-cavity limit.The self-correlation and cross-correlation characteristics of photons can be effectively controlled by adjusting system parameters such as the distance between nanoparticle and QD,nanoparticle radius,frequency detuning,and relative polarization direction.In addition,this scheme has advantages such as requiring relatively small coupling strength,easily adjustable parameters,and robustness to the quality factor of the cavity,dissipation of nanoparticles,and dephasing rate of QDs.This makes the scheme advantageous for the generation of single-photon sources and has potential applications in fields such as quantum information and quantum communication.