| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 107 === Passively Q-switched solid-sate lasers are playing an important role in many applications, such as medical system, laser ignition, material processing. Simultaneous Q-switching and mode-locking is of great interest for the generation of high peak power and ultrashort pulses. However, simultaneous Q-switching and mode-locking induces severe fluctuation of peak-to-peak amplitude which is unwanted for many applications. In this thesis, we propose some methods to avoid self-mode-locked operation in a passively Q-switched Nd:YAG solid state laser. First, based on spatial hole burning effect, we reduce the the number of longitudinal lasing modes by increasing the distance between the gain medium and the front mirror. Experimental results reveal that self mode-locking effect can be suppressed slightly. Moreover, to achieve more stable peak power, we use an external feedback mirror to set a coupled cavity. We experimentally find that self mode-locking effect can be eliminated significantly. Finally, we generate different pulse energy from 0.9 mJ to 0.5 mJ by using saturable absorber with different initial transmission from 24.1% to 46.9% , respectively.
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