Comparative Study Of Characteristics Between Ultraviolet And Near-infrared Ultrafast Laser Induced Plasma Grating

In the past few years, a lot of researchers of the world investigate into plasma grating, and considerable attention has been attracted to the research of plasma grating. Many ach icvement s arc about near-infrared (IR) plasma grating. We can get a plasma grating appears in the air by optical interference modulation spatially through two crossed ultraviolet(UV) lasers. If the wavelength is different, grating parametersN electron density and diffraction of plasma grating will be different. We will know dynamic processes and its application based on plasma grating by filamentation through the differences between UV and IR plasma grating.In our experiments, we get harmonic conversion in BBO crystal by the method of doubling-compensation-tripling in a collinear device, so we can obtain efficient doubling efficiency, the wavelength and power of UV laser are276nm and10GW. It is convenient to research on the plasma grating which is conformed by two crossed UV lasers.Contrasting to IR plasma grating, the electron density in the UV plasma grating is much higher. So plasma grating is a characteristic of the researches on the ultrashort laser. We have make a study of electron density,grating thickness,the width of fringes and diffraction efficiency of the UV.plasma grating by mJ-UV lasers. Contrasting all these parameters between UV plasma grating and IR plasma grating, we will know great superiority of UV laser in optical physics research and we can provide valuable date for further research on the UV plasma grating.The contents of this thesis are following:Firstly, spatially intensity modulation is generated by the interference of two crossed UV lasers, a periodic intensity distribution is appeared in the subrange of crossed section, that is UV plasma grating. We primary study the thickness and width of fringe of grating, moreover, we also pay close attention to the relationship between delay, polarization and these two parameters.Secondly, a FW interacts with the plasma grating from the side, we find that diffraction effect appears of the FW. So we study on the features of grating diffraction, and we also calculate the electron density in the grating through diffraction efficiency.Finally, we also investigate into IR plasma grating additionally, we compare and analyze some important properties about UV and IR plasma grating mainly.Through comparative study in UV and IR plasma grating, we can know that thickness and width of fringe of UV plasma grating are thinner than IR plasma grating, and the electron density of UV plasma grating is two orders of magnitude higher than that of IR plasma grating.