低对称性非线性光学晶体硼酸铋(BIBO)的1064nm三倍频性质

Third Harmonic Generation Property of 1064 nm in Nonlinear Optical Crystal BiB_3O_6 of Low Symmetry

采用高温溶液法成功生长出高光学质量的硼酸铋 (BIBO)晶体 ,尺寸达到 2 4mm× 19mm× 35mm ,质量为4 8g。对BIBO晶体进行了定向 ,并测量了该晶体的主轴折射率。讨论了BIBO晶体的 10 6 4nm三倍频性质 ,包括相位匹配角、有效非线性光学系数deff、容限角、走离角等。结果表明 ,BIBO晶体的最佳三倍频方向为 (137.7°,130°) ,其有效非线性光学系数值达到 3.6 0 pm/V ,属I类相位匹配。就主平面内的相位匹配方向而言 ,(14 6 .4°,90°)具有最大的有效非线性光学系数值 ,为 3.16pm/V。在 10 6 4nm的腔外三倍频实验中 ,(14 6 .4° ,90°)BIBO晶体的转换效率达到 39.5 % ,角度容限半宽为 0 .2 2mrad·cm ,该数值与 0 .175mrad·cm的计算值基本符合。由于(33.6°,90°)BIBO晶体的有效非线性光学系数较小 (0 .31pm/V) ,其三倍频转换效率小于 5 %。

By high-temperature solution method, BIBO crystal with high optical quality is grown out successfully. The size reached 24 mm×19 mm×35 mm, and the weight is 48 g. For BIBO crystal the orientation, as well as the refractive index on the main optical axis, is measured. The third harmonic generation (THG) property of 1064 nm in BIBO crystal, including phase-matching (PM) angle, effective nonlinear optical coefficient (d eff), angler acceptance, and walk-off angle is discussed. The results show that the optimum configuration for the THG of 1064 nm in BIBO crystal is at the Type-I PM direction (137.7°,130°), which has a d eff of 3.60 pm/V. Among PM directions located in principal planes, (146.4°,90°) has the largest d eff value, i.e. \{3.16 pm/V.\} In extra-cavity THG experiments of 1064 nm, the conversion efficiency of \{(146.4°,90°)\} BIBO crystal reached 39.5 %, and the half-width of its angular acceptance is measured to be \{0.22 mrad·cm,\} which is in good consistent with the calculated value, \{0.175 mrad·cm.\} For \{(33.6°,90°)\} BIBO crystal, because the d eff is very small \{(0.31 pm/V),\} its THG conversion efficiency is lower than 5%.