Effect Of Exciton Dipole Moment Direction On Strong Coupling In Metal Plasma Optical Microcavity

Light-matter interaction has attracted many attentions,because it can be used for many potential applications,such as quantum device,quantum computing and quantum communication.However,strong coupling can be only realized on the conditions of ultra-low temperature and high vacuum in the previous studies,which seriously restricted the application and development of this field.Consequently,it is of great significance to realize the strong coupling interaction at room temperature.Plasmonic microcavity can realize the collective vibration of free electrons and restrict quantum photon into the microcavity,which can make the strong coupling interaction available at room temperature.Compared to the collective effects of many excitons,strong coupling based on a single emitter can approach quantum effect to avoid the indirect/off-resonant coupling of other emitters overlapping the plasmon modes.Therefore,reaching the quantum optics limit of strong coupling between a single quantum emitter and a plasmon mode is one of the fundamental goals of nanooptics.However,the strong coupling based on a single emitter system requires greater field enhancement effect,thus it is of great demands to build nano-optical device with higher sensitivity.In addition,the coupling strength is proportion to the electric field and dipole moment of emitter(g ∝<E·μG>2,where g is the coupling strength,E is the electric field,and μG is the dipole moment of emitter).The previous researches are mainly focused on the control of the electric field E of nanocavities.Few study on the control of dipole moment of emitters has been reported because of the processing accuracy and the limitation of experimental conditions.This dissertation is focused on the construction of novel metal plasmonic nanocavity based on the ’bottom-up’ method.The gold nanoprism(AuNPR)is synthesized by wet chemical method,and precisely positioned to the DNA origami via base complementary pairing.With the excellent addressability and programmability of DNA origami,we successfully constructed the nano-optical device with controllable position and determined orientation of single molecule,and systematically explore the influence of the dipole moment of emitter on strong coupling.This dissertation is divided into two sections:1.The construction of novel plasmonic nanocavity with determined dipole moment of emitterWe successfully constructed the novel plasmonic nanocavity with controllable position and determined orientation of single molecule by DNA origami technique.The DNA origami technique routinely enables the assembly of molecules with high positional accuracy,which can avoid the molecular quenching effect.Additionally,we apply DNA origami technique to accurately control the orientation of single Cy5 molecules via covalently linking Cy5 intra ssDNA(int Cy5-ssDNA).By aligning the int Cy5-ssDNA along lines of DNA scaffold or locating the int Cy5-ssDNA at the crossover site on DNA origami,the orientation of single Cy5 molecules can be controlled in a fixed horizontal or vertical orientation relative to the electric field of AuNPR.Atomic Force Microscope(AFM),Transmission Electron Microscope(TEM),and Scanning Electron Microscope(SEM)images have shown that the constructed plasmonic nanocavity matched well with our design.2.The study of the influence of the emitter dipole moment on strong couplingWe studied light-matter interaction in photoluminescence(PL)spectra with determined orientation of single or two molecules at room temperature.Our approach introduces a straightforward way to construct the plasmonic nanocavity with controllable position and determined orientation of emitters,and realizes the tunable coupling strength by controlling the dipole moment and the number of emitters.The preliminary result shows that the mode splitting can be observed in PL spectra for two Cy5 molecules system,which satisfies the strong coupling criterion.In summary,we have developed a technique to determine the orientation of fluorescent Cy5 molecules covalently incorporated into DNA origami structures.We applied this approach to study the influence of the orientation of emitter on light-matter interaction in PL spectra.Our work is significant for fine-tune the light-matter interaction by elaborately controlling the transition dipole moment of molecule,and will enable the design and fabrication of highly efficient nanophotonic devices.