Preparation Of Whispering Gallery Mode Microcavities And Study On The Generation Mechanism Of Kerr Optical Frequency Combs

In recent years,the optical microcavity based on the whispering gallery mode has attracted more and more attention from scholars at home and abroad.Optical microcavities can greatly enhance the interaction strength between light and matter by resonating the internal light field,making it relatively easy to generate various nonlinear effects.For example,low-threshold Brillouin lasers,low-noise optical frequency combs,and soliton optical frequency combs from megahertz to terahertz have broad application prospects in the fields of microwave photonics,optical communications and quantum communications,precision measurement,laser radar,coherent ranging,etc.An optical frequency comb is a set of discrete equidistant spectra that can measure frequency like a ruler.In particular,the Kerr frequency comb based on optical microcavities discovered in 2007 has revolutionary significance in this field.Another feature of the Kerr frequency comb is that once it stabilizes in a soliton state,the soliton optical frequency comb will have lower phase noise,wider frequency comb bandwidth covering from microwave to terahertz regions,and other advantages.The main work of this thesis is to prepare magnesium fluoride and silica microcavities in experiments and study the generation of Kerr frequency combs based on optical microcavities,comparing the performance of microcavities made of two different materials.Firstly,the paper introduces various parameters of optical microcavities and the dynamic process of Kerr frequency combs based on microcavities.Due to the good prospects of soliton optical frequency combs in practical applications,we focus on the dynamic process of soliton optical frequency comb formation in particular.Secondly,the paper analyzes the prerequisite conditions for soliton state formation based on numerical simulation.Thirdly,we accurately measured the quality factor and second-order dispersion of the microcavity in experiments using a calibrated MachZehnder interferometer,which is a key step in evaluating whether a prepared microcavity can be used for subsequent experiments.Next,we overcame the complex thermal nonlinearity effects inside the microcavity based on the "power-kicking" scheme and actively captured single-and multi-soliton states.With active control based on acousto-optic modulation,we achieved direct and fast tuning of the soliton optical frequency comb.We also accessed the breathing soliton state,which provides conditions for the study of breathing dynamics.Finally,we conducted some research on soliton crystal states based on magnesium fluoride microcavities.The novel soliton array inside the cavity is compact,orderly in time,and has constant phase,and its dynamic characteristics are closely related to avoiding mode crossing and pump power.To our knowledge,this is the first time that soliton crystal states have been generated in magnesium fluoride microcavities.