Research On Spectral And Sensing Characteristics In Optical Whispering Gallery Hollow Microcavity

Whispering gallery mode microcavities are miniature optical devices that bind light in tiny spaces in the form of total reflection,and have become a hotspot in optical fields such as high sensitivity sensing,nonlinear optics,and preparation of microwave photonic devices because of high quality factor and extremely small mode volume.The optical microcavity investigation was mainly based on microsphere cavities.Among many optical microcavities,the hollow core microcavity not only has the excellent performance,but also has the structural configuration of low usage for microfluidic monitoring and stems at both ends,which provides a good experimental platform for basic research and development in mechanics,material chemistry,and life science.However,some of the microcavity solutions suffer from low strain and temperature sensing sensitivity,weak tenability of the microcavity system,poor stability of magnetic field measurement,and single line shape of the transmission spectrum.In this article,the sensing peculiarity and spectral property were investigated in the whispering gallery hollow core microcavity coupled with tapered fiber system.The main researches are as follows.The electromagnetic field and mode coupling were analyzed in the whispering gallery mode hollow core microcavity.The spatial coupling model was established between the hollow core microcavity and the tapered fiber.The electromagnetic field and mechanical structure pattern were simulated by using the finite element method.The spatial coupling mechanism and the spectrum were analyzed under different coupling states by using the time-domain coupling mode and transmission matrix approach.The theory can be well matched with experimental results.The single hollow core microcavity assembled with solid magnetic sensitive material coupled with tapered fiber was established,which overcomes the drawbacks of poor stability and short service life of magnetic field sensors designed based on liquid magnetic sensitive the material.The experimental results show that the beam in the tapered fiber can be efficiently coupled and excited by resonant modes in the microcavity by means of the evanescent wave.The feasibility was experimentally verified with the frequency shift under the magnetic field.In addition,the Fano resonances were founded and a tunable resonance period was observed during coupling tuning region.Based on the simulations of mechanics and electromagnetic field,the whispering gallery mode double hollow core microcavity was obtained by optimizing and designing.The strain tuning scheme was constructed by designing the tapered fiber edge-coupled with the dual hollow core microcavity.The effect was investigated by different tapered fiber waist diameters.According to the mechanical property,the optimized spectrum was obtained by different coupling positions.To expand the application of hollow core microcavity,the model was established,which the hollow core microcapillary assembled with liquid metal couples with MFC.The organic combination was realized between the microfluidic channel and liquid metal.The dynamic and precise temperature control was achieved in the coupling system with the assistance of high thermal expansion coefficient materials.Fano resonance and EIT-like phenomena were generated during the modulation process.In addition,the system was multiplexed with fiber Bragg gratings to achieve simultaneous measurement.In this thesis,the properties were optimized in the hollow core microcavity.The sensitivity and spectrum diversity were improved.The application area was developed and expanded.The research of hollow core microcavity promotes the development of optical sensing,optical communication,and fast and slow light and so on.