| In recent years,micro-photonic devices have developed rapidly.This kind of device can realize light perception,transmission,control,and many other functions.Whispering gallery mode(WGM)microcavity is one of photonic device,it has the advantages of high quality factor,small pattern size,and light interacts strongly with matter.WGM microcavity has a good application prospect in quantum communication,nonlinear optics,extremely narrowband filtering,sensing and other fields of various physical quantities.With the gradual improvement of micro-nano processing technology,WGM has begun to miniaturization,device of the actual application direction.This paper based on the optical characteristics of echo wall cavity and sensing application related problems in the research,mainly includes the WGM cavity with the theory of optical fiber taper coupling system model,the coupling wave equation and its solution,phase/size matching problem,microsphere cavity,micro cylindrical cavity with optical fiber taper coupling with packaging technology,and the WGM cavity in the field of high sensitivity gas,refractive index sensing applications are studied.The research contents and achievements are as follows:(1)Based on the electromagnetic field theory of light wave,several key physical parameters of WGM microcavity are characterized.Based on the theoretical model of coupling between microsphere cavity and microcolumn cavity and fiber cone,the size of microcavity and the influence of coupling distance between microcavity and waveguide on coupling characteristics are analyzed and discussed,laying a theoretical foundation for subsequent experiments.The effective method of arc discharge preparation of microsphere cavity and microcolumn cavity was proposed,and the fiber cone structure with a diameter of 2 microns in the cone region and satisfying the adiabatic approximate condition was prepared by thermal method.(2)A new coupling system package scheme is proposed.The efficient and stable coupling between the microcavity and the waveguide is a difficult problem in the research field of echo wall mode.To solve this problem,we designed and produced an acrylic material base with special structure.Combined with uv adhesive,we realized the high-efficiency encapsulation of echo wall mode micro cavity without affecting the micro-cavity/fiber cone coupling system.The resonant spectrum of the encapsulated device is tested,and the results show that the encapsulation process has little effect on the coupling efficiency,and the encapsulated coupling system still maintains a high quality factor of 105.(3)According to the application demand of high sensitivity sensing field,WGM microsphere resonant cavity humidity sensor and micro-column resonant cavity ammonia sensor were trial-produced.The humidity sensitivity,long time stability and the influence of temperature on the sensor are systematically analyzed.The moisture sensitivity of calcium alginate and the feasibility of introducing humidity sensing were studied.The results showed that compared with traditional moisture sensitive materials,calcium alginate had better moisture sensitivity,stable structure and high temperature resistance.Based on this,a calcium alginate coated microsphere resonant cavity humidity sensor was proposed,and the influence of FSR,Q value characteristics and coating thickness on Q value of the sensor resonance spectrum was analyzed.According to the characteristic of low concentration ammonia detection and requirements,was proposed based on the silicone coating micro column cavity type ammonia gas sensor,and the response time of sensors,spectrum drift,stability and repeatability performance is analyzed and discussed,the results show that the sensor can achieve high sensitivity detection of ammonia in the air. |
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