Active Control Of Strong Coupling Between Plasmonic Nanocavities And Quantum Emitters

In recent years,Exploring the strong light-matter interaction between quantum emitters(atom or molecule)and plasmonic nanocavities claim much attention in the quantum science community.The system enters the strong coupling regime when the rate of coherent energy exchange between a cavity photon and an electronic transition is more significant than its fundamental energy dissipation rates.The coherent energy exchange between light and matter can generate a part-light partmatter quasi-particle called hybrid polariton,which possesses the character of both light and matter.Therefore,the strong coupling system provides a novel platform to realize quantum entanglement and study novel quantum effect such as vaccum Rabi oscillation,nonlinear photon blockade and Bose-Einstein condensation,possessing great potetial in applying in quantum communication and quantum computing realm.In the field of light-matter strong coupling,huge effects have been put theoretically and experimentally to build room-temperature strong coupling system with huge coupling strenge or with countable few(even down to single)quantum emitters using metallic plasmonic nanostructures.The emphases of these study remain in the observation of stable strong coupling phenomena and fundamental research.Active control of plasmon-exciton polariton states by external stimuli is a crucial step to develop strong coupling applications such as ultrafast single photon switches,thresholdless nanolasers,high-precision biochemical sensors.However,relevant studies have rarely been reported,domestic and overseas research group are both in the start-up stage.Herein,we put our emphasis on studying the strong coupling phenomenon and its dynamic control between tailored Au@Ag nanoparticles and J-aggregates.the primary findings of our research are presented as follow:1.We utilized the chemosynthesis method to obtain metallic plasmonic nanostructures with ultra-small mode volume.Base on the molecule self-assembly technology,we realized conjugation between single/multilayer J-aggregates and Au@Ag nanorods.In the single-layer J-aggregate situation,the light-matter interaction distance is as short as 0.9 nm.We observed～198 meV vacuum Rabi splitting in the room-temperature condition,indicating the system has attained a strong coupling regime.Furthermore,we demonstrate a fine-tuning of the cavity resonance in a range of 10 nm,realized by adjusting the solvent environment refractive index around plasmonic nanocavities.The precision of our study reach is five times higher than existing methods(～1nm).The strong coupling system’s refractive index sensitivity is as high as 353.6 nm RIU-1,which opens up possibilities for ultra-sensitive biochemistry sensors.2.We introduce a galvanic deposition approach to synthesized Au@Ag nanoring structure.A homogeneous electric field was built by exciting the LSPR cavity mode,which could maximize the number of J-aggregates excitons involving in the strong coupling process.We observed a～200 meV Rabi energy splitting in room-temperature conditions.Furthermore,we use FDTD simulation and Coupled Oscillation Model to analyze the experimental data.The calculated number of Jaggregates excitons strongly coupled to single Au@Ag nanoring reach as high as 196,resulting in considerable coupling strength(～111.3 meV),which is even more significant than single Au@Ag nanorod(～87.2 meV).Our study indicated that the critical factor in enhancing the coupling is not limited to just the mode volume.Enlarging the plasmonic hotspots’ volume can increase the number of excitons participating in the coupling process,which could also enhance the coupling strength.This may provide a new method to establish strong coupling systems.3.We demonstrate a dynamic control of the strong coupling system consist of Au@Ag nanorods with ultra-small mode volume and J-aggregates in a microfluidic environment.Using a microfluidic channel to regulate the integration of J-aggregate into a single metal nanoparticle,we realize a flexible manipulation of the coupled exciton number from 0 to～3.Profit from the high concentrate plasmonic field around Au@Ag nanorods’quadrate tips and an ultrasmall mode volume as low as～91nm3,we achieved a relatively large Rabi splitting(～73.6 meV)even in the single exciton scenario.Interestingly,the measured spectral splitting ΩR is proportion to(?),reflecting the plexciton’s quantum feature.Our research provides an easily fabricated platform to manipulate plasmon-exciton strong coupling at its fundamental limit and has potential in advanced quantum optic and biosensing applications.