Research On Key Technologies Of High Repetition Rate Optical Frequency Comb

With the development of laser technology and astronomy, optical frequencycomb (OFC), as a special kind of laser source, is widely used in the fields of laserranging, spectroscopy and precision measurement. Especially in astrometry, the use ofOFC in wavelength calibration is significant for the development of modernastronomy. However, the current calibration light source from360nm to400nm isnot available, and the repetition frequency of direct output of the OFC is too low forsky survey spectroscopy with relative low resolution. In order to solve the criticalproblems above, this thesis intends to obtain390nm-centered OFC by the use offourth harmonic of1560nm-centered pulse laser with repetition frequency of36.5MHz. Furthermore, the repetition frequency is preliminarily measured and locked,and the methods to amplify repetition frequency to1GHz by Fabry-Perot (F-P) filtertechnology are studied. The thesis studies the basic technologies for obtaining360nm-400nm standard light source which can be used in astronomical spectrographcalibration. The main contributions were as follows.1. Laser pulse generation and amplification experiments. Femtosecond pulsedlaser was generated by the nonlinear polarization rotation clamping method,and the center wavelength, spectral bandwidth and the power of output laserwere measured. The pulse width was measured with autocorrelation method.According to the research on theories and methods of energy amplification,the energy of original pulse laser was experimentally amplified nearly1,300times with Erbium-doped fiber amplifier.2. Laser fourth harmonic generation experiment. According to optical nonlineartheory,390nm-centered laser was obtained by laser fourth harmonicgeneration experimental system from the original1560nm-centered pulsedlaser by BBO crystal.3. Preliminarily research on locking of OFC and repetition frequencyamplifying and filtering with F-P filter. Theories and methods on OFCgenerated by repetition frequency locking and repetition frequencyamplifying with F-P cavity were studied. The difference frequency signalbetween repetition frequency and standard frequency from frequency synthesizer was detected, and the stability of repetition rate was obtainedwith comparison to standard rubidium clock signal. A temperature controlbox for laser oscillator was experimentally built with temperature controlaccuracy of0.1℃.The thesis studied the problems currently existing in applying OFC toastronomical wavelength calibration, and proposed the solution to the problem.Theoretical studies to the related technologies construction of the main body of theexperimental system, and design of the experimental system parameters werecompleted, which laid the foundation for the realization of the system.