The Detection Of The Carrier-envelope Offset Frequency In Yb-doped Femtosecond Optical Frequency Comb

Optical frequency comb can dramatically simplify optical frequency measurement and improve its precision. It also provides an effective way for precision spectroscopy and fundamental physical constant measurement. In order to realize the precise control of optical frequency comb in both time and frequency domain, the carrier-envelope phase offset frequency in optical frequency comb needs to be detected precisely. Based on a home-made Yb-doped femtosecond optical frequency comb system, this thesis carried out a theoretical and experimental study on supercontinuum broadening in photonic crystal fiber. Besides, the carrier-envelope phase offset frequency(f_COE) in optical frequency comb was successfully detected by utilizing different beat note measurement setups. In general, the main contents of this thesis are as follows:First, supercontinuum generation in photonic crystal fiber was numerically simulated using split-step Fourier method. The effective refractive indices of two kinds of photonic crystal fibers, SC-5.0-1040 PCF and NL-2.3-850 PCF, were obtained by utilizing finite element analysis in COMSOL Multiphysics. The dispersion curve and the propagation constant ? were calculated. By solving nonlinear schrodinger equation in MATLAB, supercontinuum generation in these fibers were simulated. Particularly, for SC- 5.0-1040 PCF, the influences of the fiber length and the input power on supercontinuum generation were discussed in detail. Second, optical broadening covering the spectral range from 500 nm to 1200 nm was obtained in the NL-2.3-850 PCF, while this range is 756nm-1335 nm for the SC-5.0-1040 PCF and 610nm-1300 nm an octave supercontinuum was achieved from the tapered PCF. Simulation results of two PCFs are basically consistent with experimental results. Last, the beat note measurement setups using self-referenced f-2f technology were built and tested. For one thing, the beat note measurement setup based on NL-2.3-850 PCF realized 31 d B 1) signal-noise ratios. For another thing, the setup based on SC-5.0-1040 PCF?tapered? was improved through the theoretical calculation and experimental optimization, which makes the final 1)signal-noise ratio increase from 27 d B to 37 d B.The experiment lays a solid foundation for the further research on frequency stabilization and precise control of optical frequency comb.