Measurement Of Ultra-stable Optical Cavity’s Parameters And Influence Of Current White Noise Upon DFB-LD’s Laser Linewidth

High finesse ultra-stable optical cavity can provide high-precision frequency standard and fine frequency resolution,the construction of ultra stable narrow linewidth laser system based on high-precision ultra stable optical cavity and PDH frequency stabilization technique is becoming mature,which can effectively narrow the laser linewidth and suppress phase noise.High finesse ultra-stable optical cavity has developed into an important tool for preparing high-quality light sources,playing an important role in optical frequency atomic clock,quantum precision measurement and other fields.As the core component of the ultra-stable narrow-linewidth laser,we are committed to pursuing a high-finesse optical cavity with high stability and low loss experimentally.Through the improvement and optimization of the polishing and coating of the substrate,ultra-low expansion coefficient materials,the selection of the cavity geometry and parameters,the support and suspension of the cavity,precision temperature control,vacuum technology and other aspects,the fineness of the optical cavity can now reach the order of a million or higher,and the thermal expansion coefficient can reach a level of 10^-8/K or even lower.Cavity length,cavity linewidth,free spectral range,cavity finesse,zero expansion temperature are important parameters of high-finesse optical cavity,it is particularly important to use certain measurement methods to measure them accurately in practical applications.Laser linewidth,as an important parameter for the experimental study of the interaction between light and atoms,has a relatively complete theoretical and experimental researches.In order to meet the development of precision laser spectroscopy and the ultra-stable narrow-linewidth laser system based on the ultra-stable optical cavity and PDH frequency stabilization technique,experiments often focus on the pursuit of narrower linewidth laser.The broadening of diode laser linewidth by injecting current’s white noise can be intervened and adjusted according to experimental requirements,which opens up a new possibility for research in laser communication,laser measurement,precision spectroscopy and other fields.Its advantage of adjustable coherence length has great potential for the generation and optimization of interferometric fiber optic gyroscope,chaotic laser,and etc.In this thesis,we first introduced two sets of ultra-stable optical cavity systems used in our laboratory for single photon transition and cascaded two-photon transition coherent excitation of cesium atoms from ground state to Rydberg state.We measured the relevant parameters of ultra-stable optical cavity through radio frequency modulation side-band and cavity ring-down methods.Using saturation absorption spectroscopy（SAS）and modulation transfer spectroscopy（MTS）as frequency reference,we obtained two sets of ultra-stable cavity’s zero expansion temperature points through the change of the resonant frequency of the ultra-stable cavity under different temperature.Then,the linewidth broadening of DFB-LD with current white noise are experimentally studied by using the high-finesse F-P cavity linewidth measurement method and the fiber-delayed and acousto-optic modulator-shifted self-heterodyne method.For narrower laser linewidth（<k Hz）measurement,In view of the limitations of traditional laser linewidth measurement methods for narrower linewidth measurement,the feasibility of self-heterodyne scheme based on short fiber-delayed is simulated and verified.