Preparation And Application Of Whispering Gallery Mode Optical Microcavity

In recent years,the whispering gallery mode optical microcavity with the characteristics of high-quality factors?Q?and low-mode volume?V?have attracted attentions of many researchers.The Whispering-gallery Mode?WGM?refers to that when a specific wavelength of light waves in the cavity by high refractive index of the medium into low refractive index of the medium cause total reflection and the optical path is equal to the phase matching condition wavelength integer times,the discrete resonant modes with equal intervals occur.Such electromagnetic field mode is called WGM.The development of micro-nano optical technology makes WGM microcavities with super high quality factor,very low component volume,easy to integrate and so on.The WGM microcavities is used as an important optical component in various fields,such as cavity quantum electrodynamics,nonlinear optics,low-threshold laser,high-sensitivity sensor and optical filter.This paper studied the whispering-gallery mode optical microbubble or microbottle in theory and experiment.Detailed research contents include the following:Firstly,this paper reviewed the history of whispering gallery mode optical microcavities,then introduced three kinds of classification of microcavity and application.Secondly,starting from Maxwell's equations deduce the eigen modes of microsphere cavity in theory,get the basic parameters of whispering gallery mode microcavities,including of quality factor?Q?,mode volume?Veff?and free spectral range?FSR?.Then this paper introduces a finite element simulation method,using COMSOL Multiphysics softwave simulation analysis mode and refractive index sensing properties of capillary microbottle with surface curvature changes in equatorial plane.Studying the mode characteristics of microbottles with different surface curvature and expansion radius,then discussed the energy percentages of core with different modes under different surface curvature,finally analyzed the refractive index sensing characteristics of microbottles.The results show that,the influence of the second tangential mode is more obvious than the first mode when surface curvature changes,the square of curvature inside surface?k₂² is 0.008?m^-22 with quality factor over 10⁸.With smaller curvature inside the surface,more percentage of light intensities in core of microbottle and high sensitivity refractive index can be achieved.Then set up an experimental system in which use 30%concentration of hydrofluoric acid solution be inject through capillary 40 minutes by injection pump to obtain microcapillary with wall thickness 10?m,and the speed of corrosion0.25?m/min.Meanwhile the experiment platform also can get different wall thickness of the capillary.Using the way of electric spark discharge preparation of quartz capillary microbubble,and analyzed the influence of the capillary placed position between the electrodes on the formation of microbubbles.In the end,quartz capillary microbubble with better sphericity and diameter of 240?m were made.Finally,quartz capillary microbubble coupling experiments were carried out.A experimental system of tapered optical fiber made was built,the tapered optical fiber with diameter less than 3?m was fabricated by using hydrogen and oxygen flame as heat source and use stepping motor.Using tunable semiconductor lasers to output1550 nm communication band as light source,low noise detectors and oscilloscopes collect and display transmission spectra,build a micro-bubble and tapered optical fiber coupling platform,adjust the coupling distance to excite a variety of WGM.The measured data of quartz capillary microbubble cavity near the peak value of1557.087nm were fitted.The quality factor Q is 1.9×10⁵,and the free spectrum range FSR is about 2.2nm.It has very good application prospects.