| Most of waveband of ultra-short laser is concentrate on mid-infrared and infrared, but there are more potential applications of short-wavelength and broadband frequency laser. At present, the frequency conversion is an accessible way to obtain short-wavelength ultra-short laser. Therefore, harmonic generation has been studied widely as a critical technology in the research of short-wavelength ultra-short laser. The conversion efficiency and the beam quality are two main contents in research of harmonic generation of ultra-short laser. In order to increase conversion efficiency and improve the beam quality, it is necessary to study on the physical factors affecting the conversion efficiency of harmonic generation and the beam quality of harmonic generation field. For these reasons, this thesis focuses on conversion efficiency and beam quality. The main results obtained here can be summarized as follows:1. The physical model of the frequency doubling and tripling in a single crystal of ultra-short laser, which includes group-velocity mismatch and dispersion, self- and cross- phase modulations, and the absorption of crystal etc., has been built up. The numerical calculation code of harmonic conversion of ultra-short laser has been given and verified to show the validity and reliability of our code.2. Second harmonic generation of ultra-short laser in KDP crystal has been studied. The effects of the pulse width and intensity of fundamental field, the... |
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