Fabrication And Sensing Properties Of Silica Capillarys Microbubble Optical Microcavities

In recent years,the whispering-gallery mode optical microcavities with high-quality factors(Q)and low-mode volume(V)has attracted attentions of many researchers.The Whispering-gallery Mode(WGM)refers to that the light is restrained inside the cavity and circulating around the equatorial plane when it is traveling inside a cavity by total reflection.When the length of the optical path is an integer multiple of the wavelength,that's to say,when meets the phase matching requirements,the discrete resonant modes with equal intervals occur.Such electromagnetic field mode is called WGM.The WGM microcavities is very small in size as well as easily integrated,and the energy density inside the cavity is extremely high.Moreover,the manufacturing process is easy and simple with low cost.With above properties,the WGM microcavities is used as an important optical component in various fields,such as low-threshold laser,optical filter and high-sensitivity sensor.Resonant frequencies of WGMs are also highly inflenced by external factors and this leads to ultrahigh sensitivity in sensing applications.More and more alternative designs of whispering gallery mode resonators have been proposed and developed in recent years,with improved senstivity and resolution limits beingpursued,Liquid core optic ring resonator sensors are an akternative type of WGM resonator.Such devises can be viewed as hybird microresonators,since the evanescent light field can penetrate into the liquid in the core.In Liquid core optic ring resonator sensors,however,a high Q is maintained because most of the WGM energy still propagates in the shell structure.This paper studied the whispering-gallery mode optical microbubble in theory and experiment.Detailed research contents include the following:Firstly,this paper reviewed the research background and progress of whispering gallery mode optical microcavities in recent years,and gave a brief introduction of the application situations of whispering-gallery mode optical microcavities with specific cases.Secondly,it introduced the mode theory of the whispering gallery mode optical microcavities and the tapered optical fiber.Through Maxwell's equations and the boundary conditions of ellipse-microbubble,it analyzed the modes distribution inside the ellipse-microbubble,and gave a brief introduction of the basic properties of ellipse-microbubble.Numerical simulations of the modes inside the ellipse-microbubble were conducted by the method of finite element numerical analysis provided by COMSOL Multiphysics,a kind of commercial software,and thus the distributions of WGM at the equatorial planes of the differert diameter ellipse-microbubble were obtained.senstivity and resolution of Liquid core ellipse-microbubble resonator sensors analys provided by COMSOL Multiphysics,of the differert diameter ellipse-microbubble were obtained.The characteristics of tapered optical fiber is discussed using the method of ray optics.Furthermore,COMSOL Multiphysics was used to simulate the optical field distributions on the cross sections of optical fibers with different fiber core diameters,and thus their optical field distributions were obtained.Takeing the coupling system of tapered optical fiber and ellipse-microbubble as a whole,weanalyze the coupling theoretical foundation.Then set up an experimental system in which HF be inject through capillary by injection pump to obtain different shell thickness microcapillary.Designing an experimental system for the preparation of tapered microcapillary with high-temperature melting technique and cooling method,we apply a carbon dioxide laser to heat and melt microcapillary to prepare tapered microcapillary.Ellipse-microbubble are made by locally heating a fused microcapillary wih a CO2 laser or arc doscharge while internally pressurizing the cavity.Designing experimental system to prepare Ellipse-microbubble with different diameters(120-300 m).last,set up an experimental system in which hydrogen flame heating method is used to prepare tapered optical fiber,and prepare a tapered optical fiber that is needed in the experiment and has a diameter on the level of micron dimension.Establishing a coupling system of tapered optical fiber and ellipse-microbubble or microcapillary with broadband light source,opticalspectrumanalyzers and CCD monitoring device were used to measure the quality factor and sensing properties of ellipse-microbubble or microcapillary.