The Coupling And Manipulation Between Metallic Micro-nano Structures And Excitons

Surface plasmon is the surface local electromagnetic wave mode generated by the collective oscillation of electrons on the metal surface.Since the surface plasmon can break the optical diffraction limit and can also produce strong near-field enhancement effect,the metallic micro-nano structures which supports plasmon modes offers possibilities to enhance the interaction of light and matter breaking the diffraction limit.The study of the coupling between metallic micro-nano structures and excitons is not only a basic physical topic,but also can promote applications in biomedical detection,micro-nano optoelectronic device integration,and quantum information processing,so it has important theoretical and application values.The interaction between plasmon and exciton in metallic micro-nano structures can be divided into two cases of weak coupling and strong coupling according to the strength of the interaction.In the case of weak coupling,the interaction of the exciton with the local light field will change the rate of energy exchange between the photon and the exciton,but will not change the energy level of the exciton and surface plasmon mode;In the case of strong coupling,the energy exchange rate between the exciton and the local light field exceeds the energy loss rate of the system.In this case,an apparent energy level splitting(called Rabi splitting)will occur in the system,and makes the system energy to generate periodic oscillations(called Rabi oscillations).Due to its unique properties,strong coupling is an ideal platform for studying fundamental quantum mechanics problems such as quantum entanglement and Bose-Einstein condensation(BEC),and also provides great potential in applications such as low-threshold lasing,regulation of chemical reactivity,and quantum-optical devices.In this thesis,we systematically study the coupling between excitons and several types of metallic micro-nano structures such as metallic micro-nano arrays,metallic micro-nano waveguides,and single metallic nanocavity.The strong coupling between plasmon and exciton is achieved,and the strong coupling between plasmon and exciton can be manipulated in various methods.The main research contents and innovations of this thesis are as follows:1.A gold nano-disk array structure is proposed.The array structure supports two plasmon modes:one is the local surface plasmon(LSP)mode supported by the gold nano-disk,and the other is the propagating surface plasmon(SPP)mode supported by the periodic structure.The strong coupling effect will be generated between the two modes and a new hybrid mode will be generated when the detuning between the SPP mode and the LSP mode is small.Based on this,the multimode strong coupling between plasmon and excitons is achieved by adding J-aggregate molecular layers on the nanoarray structure and adding Fabry-Perot microcavity.The manipulation of strong multimode plasmon-exciton coupling is realized by changing the diameter of the gold nano-disk and the cavity length of the Fabry-Perot microcavity.2.The strong coupling between MIM waveguide structures and excitons is discussed.Strong plasmon-exciton coupling is achieved in the side-coupling cavity system by filling the groove-shaped cavity with J-aggregate molecules,and the strong coupling is manipulated by changing the background refractive index.By extending the system to a dual-slot resonator coupling system with J-aggregate molecules,strong plasmon-exciton multimode coupling is achieved,and manipulation of strong multimode plasmon-exciton coupling is realized by changing the background refractive index and the oscillator strength of excitons.3.The multimode coupling between two different excitons in J-aggregates and WS2 two-dimensional materials with a single silver ring nanocavity is studied using theoretical and numerical simulation methods.The normalized scattering spectra of the Ag-J-aggregates-WS2 hybrid system are calculated using the finite-difference time-domain method(FDTD)and the theoretical coupled oscillator model,and they are matched well.The multimode strong coupling manipulation of the Ag-J-aggregates-WS2 hybrid system is achieved by changing the ambient temperature and the oscillator strength of the excitons.4.A structure based on silver nanocube dimer is proposed,which has an ultrasmall mode volume and can achieve ultrastrong coupling with excitons.Analysis find that the structure supports two different modes,so double strong coupling and manipulation can be realized in the system by the interaction between two different modes and excitons.According to theoretical calculations,the number of excitons involved in the strong coupling is no more than 10 which is close to the quantum optical limit,indicating that the system may have potential applications in fields such as quantum information processing.