坩埚下降法沿＜０１０＞和＜００１＞方向生长了直径达到２５ｍｍ的完整透明的Ｃａ４ＹＯ（ＢＯ３）３ （ＹＣＯＢ）晶体．化学腐蚀结果表明，所生长晶体无孪晶或亚晶界等缺陷，晶体尾部的位错密度 不超过１８００／ｃｍ２测量了ＹＣＯＢ的透射光谱，其截止波长为２００ｎｍ进行了ＹＣＯＢ晶体对 Ｎｄ：ＹＡＧ激光的二次倍频实验．通过与ＫＤＰ晶体对比，计算出ＹＣＯＢ晶体的有效非线性系数 在Ⅰ型相位匹配方向（θ，φ）＝（６６．３°，１４３．５°）和（６５．９°，３６．５°）上分别为１．４５ｐｍ／Ｖ和０．９１ｐｍ／Ｖ； 大于ＫＤＰ和 ＬＢＯ晶体．在脉冲宽度１０ｎｓ的 Ｎｄ：ＹＡＧ激光单脉冲辐射下ＹＣＯＢ晶体出现体 损伤的激光损伤阈值不低于８５ＧＷ／ｃｍ２．
Crack-free and transparent Ca4YO(BO3)3 (YCOB) crystals with 25 mm diameter were grown by
the vertical Bridgman method in <010> and <001> directions. The results of chemical etching indicate that there are no sub-boundaries or twins
in the crystal, and the density of dislocations observed at top region of a crystal is less than 1800/cm2. The measured transmission spectrum
shows that the crystal has wide transmission range with absorption edge at 200nm. The SHG of a Nd:YAG laser was performed for YCOB crystals in
comparison with KDP crystal, the effective nonlinear coefficients (deff) of YCOB in type I phase matching directions of (θ, φ)=(66.3℃,
143.5℃) and (65.9℃, 36.5℃) were estimated to be 1.45pm/V and o.91pm/V respectively. The bulk damage threshold was observed as
85GW/cm2 for single pulse of a Nd:YAG laser with 10ns pulse duration.
参考文献
| [1] | Norrestam R, Nygren M. Chem. Mater., 1992, 4: 737--743. [2] Iwai M, et al. Jpn. J. Appl. Phys., 1997, 36: L276--L279. [3] Kobayashi T, et al. Proceedings of International Symposium on Laser and Nonlinear Optical Materials, Singapore, 1997. 317--319. [4] Ye Q, Chai B H T. J. Crystal Growth, 1999, 197: 228--235. [5] 宫波, 等. 人工晶体学报, 1999, 28: 31--36. [6] Chen C T, et al. J. Opt. Soc. Am. B, 2000, 17 (4): 566--571. [7] Dmitriev V G, Gurzadyan G G, Nikogosyan D N. Handbook of Nonlinear Optical Crystals (2nd edition). Berlin: Springer-Verlag, 1997. 78--85. |
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