The Fabrication And Dispersion Control Of Whispering-Gallery Mode Microcavity

In optical research,optical microcavities are an important research tool with a wide range of applications.In recent years,the whispering gallery mode?WGM?microcavity with ultra-high quality factor and ultra-small mode volume has been widely concerned by many scholars.The whispering gallery mode means that light coupled into the microcavity propagates in the microcavity by means of total reflection,and when the phase matching condition is satisfied,a resonant mode of equal frequency spacing is generated.The whispering gallery mode optical microcavity has been deeply studied in applications such as high sensitivity sensors,ultra-narrow linewidth filters,and Kerr optical combs.This thesis mainly studies the preparation,testing,dispersion control and nonlinear optical application of WGM optical microcavity.Combined with theory and experiment,the main work is as follows:1.The related theory of WGM microcavity is introduced,and the silica rod is melted by CO₂ laser to form WGM microrod cavity.A tapered fiber with a transmittance more than 90%was prepared.Based on this,the near-field coupling of the tapered fiber was used to complete the efficient coupling of the WGM microrod cavity.The microcavity coupling test platform was built to deeply test the physical parameters of the WGM microrod cavity.By adjusting the fine annealing method in the CO₂ laser processing process,the Q value of the WGM microrod cavity was raised to 10⁸.2.In order to apply the prepared microrod cavity to the generation of Kerr optical frequency comb,it is necessary to understand the dispersion curve of the microrod cavity,and the modulation instability phenomenon can only be satisfied in the anomalous dispersion region.By using COMSOL multiphysics to simulate the microcavity mode field distribution,the dispersion curve is calculated.Meanwhile,through the experiment to understand the dispersion of the micro-cavity,and verify the correctness of the COMSOL simulation.3.The experimental platform was built to test the nonlinear optical application of WGM microrod cavity.The experimental phenomena such as degenerate four-wave mixing effect,modulation instability,cross-phase modulation and self-phase modulation were observed.Finally,a Kerr optical frequency comb with a bandwidth of 40 nm was successfully produced in the WGM microrod cavity.In addition,Raman scattered light was experimentally observed by the stimulated Raman scattering of photons and silica molecules in the WGM microrod cavity.