Ultrashort Laser Pulses And Cslib <sub> 6 </ Sub> O <sub> 10 </ Sub> Crystal Optical Properties Of The Interaction

We have studied theoretically the optical properties of the interaction between ultrashort pulses and the nonlinear optics crystal cesium lithium borate (CsLiB₆O₁₀). In the picosecond and femtosecond time field, the durations of the pump and signal pulses are so short that special propagating characteristics of ultrashort pulse laser should be taken into account, especially the pulse broadening induced by the group velocity mismatch and the group velocity dispersion. We all know that the output of ultraviolet (UV) laser mostly depends on the conversion of nonlinear frequency, thus a new kind of excellent nonlinear optics (NLO) crystal is very important for the output of new wavelength. Compared with the usual crystals, such as KH₂PO₄ (KDP) , β -BaB₂O₅ (BBO) and LiB₃O₅ (LBO) , the CLBO crystal provides larger effective nonlinear coefficient, wider output wavelength range, smaller walk-off angle, wider permitted parameters, larger bulk crystal and many other advantages, which make it become an attractive NLO crystal for generating UV radiation. We have studied the propagating properties of ultrashort pulses in the CLBO crystal, analyzed theoretically and simulated numerically the optical parametric properties of interaction between ultrashort pulses and the CLBO crystal.In the chapter 1, we have introduced the development of ultrashort pulse laser and summarized the background and resent research advance of CLBO. In the chapter 2, we have studied theoretically the propagating characteristics of ultrashort pulses in the CLBO crystal. We have calculated and plotted the curves of the refractive index, group velocity index, lowest-order and second-order dispersion indexes as a function of wavelength. Thelowest-order and higher-order dispersion-induced broadening and deforming of light pulses is analyzed for various pulse shapes, such as Gaussian, super-Gaussian and hyperbolic secant pulses. In the chapter 3, we have analyzed and simulated the optical parametric properties of ultrashort pulses in the CLBO crystal. The phase matching and group velocity matching conditions of type-I and type-II second harmonic generation (SHG) are obtained according to the momentum and energy conservation laws. The group velocity delay of ultrashort pulse SHG on CLBO and the crystal length decided by the group velocity delay are analyzed and compared with BBO's. Second harmonic is generated by 532nm fundamental wave on CLBO, and the harmonic pulse is plotted along with the CLBO crystal length. From three-wave coupling equations, the optimal crystal length, conversion efficiency and parametric light pulse width are computed numerically when CLBO is used in picosecond optical parametric amplification. The results present that CLBO are suited for optical parametric amplification in short wave band. In order to get higher conversion efficiency, the crystal length should be optimized according to the intensities of pump and signal waves.