| Ultraviolet (UV) ultrashort pulses, which combine the characters of short wavelengths, high photon energy as well as high time resolution, have a wide spread applications in many areas, such as precision nano-machining, strong field optics, optical frequency measurements, femtosecond chemistry and ultrafast pump and probe techniques. However, since it is difficult to obtain the UV ultrashort pulses directly through the stimulated radiation, the most efficient and effective way is frequency up-conversion, which is converting infrared and visible ultrashort pulses to UV wavelength.In this dissertation, the work focused on the UV and vacuum ultraviolet (VUV) generation as well as some primary application of the UV ultrashort applications. In the beginning of the work, the frequency up-conversion was based on a commercial Ti: sapphire laser, and the deep ultraviolet (DUV), VUV and extreme ultraviolet (XUV) ultrashort pulses were obtained using different solid state mediums and gas mediums:1. BBO crystals were used in a frequency doubling-compensation-tripling scheme, and with this method, the267nm UV pulses with the output power of1.6mJ, which had a repetition rate of10Hz and pulse duration of190fs were obtained, the corresponding conversion efficiency was7%.2. The ultrashort pulses at200nm were obtained in a frequency doubling process with a KBBF crystal, in which the injecting seed-pulse was the second harmonic of the10Hz Ti:sapphire laser. The DUV pulse energy achieved0.1mJ, and the system used a pair of prisms to compensate the dispersion introduced by the upconversion crystals, thus the duration of the200nm pulses was shortened to780fs.3. The second harmonic and third harmonic of a10Hz Ti:sapphire laser were focused onto an argon target under a gas jet in a vacuum cell to achieve relatively high beam intensity, and the133-nm VUV pulses,89-nm and79-nm XUV pulses were generated within the laser-argon interaction area, with the pulse energy of6.4μJ,251nJ, and199nJ, respectively.Compared to solid state laser systems, the fiber laser system with a compact structure, low pumping threshold, good stability as well as perfect beam quality, was the robust and reliable driving source for the high repetition and high power UV pulses generation. The power amplification was essential for the generation of UV pulses, since the up-conversion efficiency was relatively low. The dissertation demonstrated a master-oscillator amplifier system combing with the chirped pulse amplification and cascade amplification, and built a multi-stage photonic crystal fiber amplifier to achieve300W output pwer with seeding pulses from an Yb: YAG ceramic oscillator with a repetition rate of103MHz. Part of the infrared output was upcon verted to258nm with two BBO crystals. The maximum ultraviolet output reached1.6W.The dissertation also demonstrated some applications of the UV pulses. The filamentary propagation of the intense267nm ultrashort pulse was studied, as well as filamentary plasma gratings formed by the noncollinear interaction of synchronized filaments. Beyond that, collisions of nitrogen and argon gas mixture with energetic electrons accelerated by Bragg incident intense infrared femtosecond laser pulses in ultraviolet filamentary plasma gratings were also investigated.In addition, new ultraviolet pulse driving sources were explored in the dissertation, such as tunable Yb:YSO laser which had a wide tuning range of110nm, providing the possibility of the tunable ultraviolet laser. The erbium-doped fiber laser (EDFL) as well as the ytterbium-doped fiber laser (YDFL) were built with the nonlinear polarization rotation method, providing the driving source for the all fiber UV-pulse generation system. |
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