Construction of a highly stable ultrafast polarization maintaining fiber based laser system ; 高穩定超快脈衝保偏光纖激光器的建設 ; Gao wen ding chao kuai mai chong bao pian guang xian ji guang qi de jian she

M.Phil. ; Ultrafast lasers have been widely used in different science and engineering areas. They provide extremely high peak power and short pulse width, which are particularly suitable for applications such as surgery, precision machining, nonlinear optics, probing chemical reactions, etc. In general, two types of ultrafast lasers are available and they are solid-state and fiber-based lasers. Although solid-state ultrafast lasers, such as titanium sapphire lasers, enjoy high power and wide spectral tuning range, they are very expensive and not affordable. On the other hand, rare-earth doped fiber-based lasers are highly compact and cost-effective. Therefore, there is a high demand in making fiber-based femtosecond lasers with high stability while at the same time providing high average power. In this thesis, we construct an ultrafast near-infrared polarization maintaining ytterbium-(Yb)-fiber-based laser system. The system uses a linear cavity configuration with proper dispersion management and the passive mode-locking is achieved by using a semiconductor saturable absorber mirror. The temporal, spectral, and energy profiles of the generated pulses are characterized systematically. Highly stable, wave-breaking free Gaussian laser pulses with energy of 0.0147nJ and pulse width of 590fs at repetition rate of 68MHz are generated. By using a highly-doped Yb fiber as pre-amplifier and a pair of transmission gratings as compressor, the pulse energy and width can be further improved to 0.662nJ and 400fs. The theoretical aspects of the ultrafast fiber-based laser system based on the formation of femtosecond pulse under the influence of dispersion and nonlinear effects are discussed. ; 超快脈衝已經被廣泛地應用在不同的科學和工程範圍。這些脈衝提供強大的峰值功率及短的脈衝寛度，這使到它們特別適合應用於手術、精準加工、非線性光學、探測化學反應等。一般來說，固體激光器及光纖激光器是兩個可用的激光器。雖然固體激光器提供強大的功率及寬闊的可調製光譜範圍，例如鈦藍寶石激光器，但它們的價格十分昂貴而我們不能負擔。另一方面，稀土掺雜光纖激光器佔用少空間以及它們的價格便宜。這使能夠供強大功率的高穩飛秒光纖激光器的需求很大。 ...