| Summary: | 碩士 === 輔仁大學 === 物理學系 === 98 === In this thesis, based on the polarization additive-pulse mode-locking technique, we successfully set up a Yb-doped fiber laser which can generate femtosecond pulse trains with the repetition rate of 40-60 MHz and the center wavelength at 1035 nm. Besides, a home-built two-photon absorption (TPA) interferometric autocorrlator is used to measure the pulse width such that the characteristics of ultrashort pulses of the mode-locked Yb-fiber laser can be identified with respect to different values of net cavity group velocity dispersion (GVD). According to the experimental results, we find that when the net cavity GVD is between 0.052 ps2 and 0.079 ps2, the Yb-doped fiber laser operates in the self-similar regime and can generate the pulse with a higher pulse energy (> 1.5 nJ). On the other hand, when the net cavity GVD is close to zero, the Yb-doped fiber laser is in the stretched-pulse regime and can generate a pulse with shorter pulse duration (FWHM < 100 fs ). In addition, the average power of the mode-locked Yb-fiber laser has been further boosted up to watt level by a chirped-pulse amplifier (CPA) based on the double-cladding Yb-doped fiber. The pulse after the CPA is with a linear chirp and can be compressed to 400 fs by the grating pair.
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