| Summary: | 碩士 === 國立交通大學 === 光電工程系所 === 97 === In this thesis, reliable Q-switched mode-locking in an Yb-doped fiber laser is demonstrated by employing an acousto-optic modulator (AOM) and a linear fiber cavity. Within the Q-switched envelope, mode-locked pulses with the repetition rate of 40 MHz can be obviously seen and their repetition rate is equal to the RF driving frequency of the AOM. In our experimental observation, the width and the asymmetry ratio of the Q-switched envelopes depend on the modulation frequency of AOM. At lower modulation frequencies, satellite pulses can be seen with their number being also related to the modulation frequency of AOM. By alternation the optical focus spot size on the AO crystal, we demonstrate that the amplitude modulation of the AOM plays the dominant role for starting the harmonic mode-locking of the laser.
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