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根据氟硼铍酸钾(KBe2BO3F2,简称KBBF)晶体最新的色散方程以及非共线匹配的条件,采用FORTAN语言变精度数值计算方法,以YAG激光器1064 nm波长入射为例,数值计算了KBBF晶体的Ⅰ类非共线倍频相位匹配角、有效非线性系数和允许角。计算结果显示:在第一象限内,存在两个匹配方向,第一个匹配方向对应的基频o光和倍频e光的匹配角范围为19.00°～89.50°,18.08°～55.20°,20.78°～72.60°;第二个匹配方向对应的基频o光和倍频e光匹配角范围分别为19.00°～55.00°,25.07°～89.75°,22.03°～72.38°。第一组匹配方向的相位匹配角范围和相应的有效非线性系数比第二组匹配方向的大,第一组匹配方向对应的允许角比第二组匹配方向小。因此非共线相位匹配结构下KBBF晶体的Ⅰ类倍频应该采用第一组匹配方向。
According to the latest dispersion equation and non-collinear matching condition of KBF2Br3F2 crystal, using the FORTAN language variable precision numerical calculation method, taking the incidence of 1064 nm wavelength of YAG laser as an example, the numerical calculation of the KBBF crystal Class I non-collinear double-frequency phase matching angle, effective non-linear coefficient and allowable angle. The calculated results show that there are two matching directions in the first quadrant. The matching angles of the fundamental frequency o and the octave e light corresponding to the first matching direction range from 19.00 ° to 89.50 °, 18.08 ° to 55.20 ° and 20.78 ° ~ 72.60 °. The second match direction corresponds to the fundamental frequency o light and octave e light matching angle range of 19.00 ° ~ 55.00 °, 25.07 ° ~ 89.75 °, 22.03 ° ~ 72.38 °. The range of phase matching angles of the first group of matching directions and the corresponding effective nonlinear coefficient are larger than the matching directions of the second group, and the allowable angles corresponding to the first group of matching directions are smaller than the matching directions of the second group. Therefore, the non-collinear phase matching structure KBBF crystal type Ⅰ frequency multiplication should be used in the first set of matching direction.