Theoretical Study On Controlling The Coupling Between Quantum Emitters And On-chip Waveguides Based On Micro-nano Optical Cavities

The proposal of quantum communication,quantum cryptography,optical chip and other quantum technologies promoted the development of single-photon experimental technology in nanostructures.The key to various quantum technologies lies in the effective control of single-photon source radiation,enabling the quantum emitter to couple to single photon transmission channel with stability,high efficiency and high directionality.In this thesis,we use plasmonic nanocavity and optical microcavity to manipulate the radiation properties of quantum emitters and coupling characteristics of emission to the on-chip optical waveguide.Our design dramatically increases the quantum emitter's radiation rate,correspondingly,ob-taining chiral coupling and unidirectional high efficiency coupling between quantum emitter and on-chip waveguide respectively in two different plasmonic nanocavity-photonic micro-cavity hybrid systems.In the study of unidirectional high-efficiency coupling between the quantum emitter and the on-chip optical waveguide,we creatively use plasmonic nanocavity to manipulate the luminescence characteristics of single quantum emitter and succeed in converting lin-ear polarized emitter radiation into the far-field circular polarized radiation in the visible light range.Futher,the emitter-nanocavity hybrid system,taken as a circular polarized light source,interacts with local circular field of nanophotonic devices and successfully achieves chiral coupling with on-chip straight waveguide and ring cavity,respectively.In the plas-monic nanocavity-ring cavity hybrid system,it is challenging for the ring cavity of a large scale to perform full-wave simulations due to computer memory and calculation time limited.Thus,we propose a ”one-time coupling” method to estimate the coupling efficiency between the nanocavity and the ring cavity,which provides a new approach for exploring the hybrid structure's optical properties with multiscale,relatively large scale and high quality factors.In the study of unidirectional high-efficiency coupling between the quantum emitter and the on-chip optical waveguide,an Au nanorod dimer coupling to a silicon nitride photonic crystal nanobeam cavity with a collecting waveguide forms plasmonic nanocavity-photonic crystal microcavity hybrid systems.A quantum emitter,where is inserted in the gap formed by the nanorods and the nanobeam,couples to microcavity-like hybrid mode.Our numeri-cal calculations demonstrate that the enhancement of the spontaneous emission rate reaches up to more than 7000 -folds.Simultaneously,the corresponding collection efficiency into a dielectric waveguide remains more than 92%.The proposed mechanism paves the way towards the development of ultra-bright and high efficiency on-chip integrated single pho-ton sources.Considering the experimental validation,the optimal design of the bent grating coupler connected to the waveguide is given for the efficient collection of light by a detector.