Study On Dispersion Equation Of Sm_0.3Y_0.7Ca₄O(BO₃)₃ Crystal Under Variable Temperature

Quasi-parametric Chirped Pulse Amplification(QPCPA)is a new technology pro-posed in recent years to realize ultra-short and intense laser systems.Currently,samar-ium(Sm)-doped YCOB is the crystal of choice for QPCPA technology because the YCa₄O(BO₃)₃(YCOB)crystal has a wide range of transmittance,a large effective non-linear optical coefficient,a high laser damage threshold,and it can strongly absorb idler light by doping with specific ions which suppress the backflow of idler light to achieve enhancement.Since the absorption of the crystal causes temperature changes,it has a certain effect on the phase matching angle of the Sm:YCOB crystal,and it will directly affect the conversion efficiency of the quasi-parametric pulse amplification.Therefore,the measurement of the refractive index of the crystal under various temperatures is car-ried out,which is quite important to QPCPA system crucial.This dissertation mainly fo-cuses on the measurement of the refractive index of Sm:YCOB crystal under various temperature conditions.The specific contents are as follows:1.The common methods for measuring the refractive index of nonlinear optical crystals and the theory of obtaining the temperature coefficient of refractive index are introduced,and the PID heating temperature control system is self-assembled to main-tain the temperature of the Sm_0.3Y_0.7Ca₄O(BO₃)₃ crystal at the set temperature within the range of 1?.The heating device is fixed on the sample platform of the high preci-sion wide-band refractive index instrument,ensuring that the entire device will not be displaced relative to the rotating sample stage,and maintaining the measurement accu-racy at 1×10^-5.2.The vertical incidence method was used to measure the refractive index n_x,n_y,n_zof the three spindles of the Sm_0.3Y_0.7Ca₄O(BO₃)₃ crystal in the wavelength range of 363?1014 nm and the temperature range of 30?100?.The experimental curves of the principal refractive index at each temperature are obtained,and the principal refractive index change curves of the Sm_0.3Y_0.7Ca₄O(BO₃)₃ crystal at each temperature are fitted,and the residual diagram of the calculated value and the experimental value is shown,and the chi-square coefficient and correlation coefficient of the fitted curve are given,which intuitively shows the degree of agreement between the fitted curve and the exper-imental value.3.The temperature coefficient of refractive index of the Sm_0.3Y_0.7Ca₄O(BO₃)₃crystal and the dispersion equation related to the wavelength and temperature of the crystal refractive index are fitted.Using this dispersion equation,the principal refractive index of the crystal at any wavelength(363nm?1014nm)and different temperatures(30?100?)can be calculated.The phase matching characteristics of the crystal at dif-ferent wavelengths on different principal planes can also be calculated,which provides basic data for studying the laser frequency conversion characteristics of the QPCPA system.