The Research Of High Third Harmonic Wave Efficiency Of Femtosecond Laser Pulse Using BBO Crystal

The ultraviolet femtosecond pulse has become a central of focus in many fields,for example,laser-spectroscopy,laser-chemistry,ICF and so on.This is due to its many advantages such as short wavelength,high quantum-efficiency,broad bandwidth,high peak-power.The conversion of ultrashort pulses from visible and near-infrared to UV is of great interest.But the high-order nonlinear effects such as Phase Mis-matching, Group-velocity dispersion affect the conversion efficiency.In the thesis third-harmonic of Ti:Sapphire is studied.The main results obtained can be summarized as follows:1.After studying the factors affecting the conversion,we design the angle and length of the BBO double-frequency crystal are 29.2°,0.2mm,correspondingly sum-frequency BBO crystal is 31.5°,0.2mm.In the experiment rebuilt TSA-25 system is used as source..2.We choose the way of non-collinear sum-frequency originating fundamental wave (800nm)and the second harmonic generation(400nm).It is reported that a proper minus Pre-Chirp introduced to the fundamental wave can interact with dispersion to improve conversion efficiency.3.In the experimental condition we also explore the optimum energy ratio for the third-harmonic generation of Ti:Sapphire.In the end,when the energies of 800nm and 400nm are 2.38mJ and 0.588mJ respectively,a single pulse energy of 230μJ at 267nm is obtained with GVD=-9.66x10~3fs~2,correspondingly conversion efficiency of 19%.