Spectrum Broadening Techniques Of Femtosecond Laser Pulses

In the past years, femtosecond laser technology has made great progress. morepeople focus on obtaining the shorter femtosecond laser pulse (mono or few cycle).The spectral broadening is the key. At present, the spectral broadening by usinghollow fiber filled with noble gas is most feasible.In this thesis, theoretical and experimental studies on spectral broadening byusing hollow fiber filled with noble gas are described. The main contents of the thesisare as follows:1. The development, progress in femtosecond laser technology andnonlinear optics, the theory of the production of ultrabroadband spectrumas well as the development of the hollow fiber were included.2. The theoretical basis of spectral broadening by using hollow fiber filledwith noble gas was explained in details, which include: nonlinearrefractive index and the effect of the Self Phase Modulation (SPM) andthe Group Velocity Dispersion (GVD) as well as the transmission of theinput pulse and the effect of the dispersion and nonlinear effect of thenoble gas.3. The analysis of the theoretical calculation result and the description of theequipment used in the experiment were included. We use themicrostructre hollow fiber and hollow fiber in Spectral broadening.Analyse the experimental results: the results are reasonable but notsatisfied. On the one hand, the width of the input pulse is not shortenough. On the other hand, there are some limitations in that equipment.Those two aspects lead to those dissatisfied results. Meanwhile thetransmission of the microstructured hollow fiber (30%) is much higherthan that of the hollow fiber (10%). We obtain the supercontinuumspectrum (400-900nm) by noble gas, and the transform-limited pulseswidth is 2.5fs.