Synthesis, Growth and Optical, Mechanical, Electrical and Surface Properties of an Inorganic New Nonlinear Optical Crystal: Sodium Cadmium Tetra Chloride (SCTC)

Abstract

A new inorganic nonlinear optical single crystal of sodium cadmium tetra chloride (SCTC) is successfully grown from aqueous solution by the slow evaporation technique at room temperature. The crystalline nature of the grown crystal is analyzed by powder X‐ray diffraction. The lattice parameters and crystal system is confirmed by single crystal X‐ray diffraction. Optical transmission study on SCTC crystal shows high transmittance in the entire UV–Vis region. The mechanical strength of the grown crystal is estimated by Vicker's microhardness test. The second harmonic generation (SHG) efficiency of the crystal is measured by Kurtz's powder technique infers that the crystal has nonlinear optical (NLO) efficiency 1.75 times that of KDP. The variation of dielectric constant and dielectric loss as a function of log frequency at various temperature reveals that the crystal shows normal dielectric behaviour. The growth process of SCTC crystal is analysed by etching study. The features of surface of grown crystal is analysed by SEM/EDAX spectrum. The third order nonlinear optical property is investigated for the grown crystal by z – scan technique and the results indicates that SCTC crystal should be a promising material for nonlinear optical device applications.

Application of Second Harmonic Generation in Characterization of 2D Materials

“…Finally, the potential research directions and prospects based 第*期 夏芳芳, 等: 二次谐波在二维材料结构表征中的应用 2 on SHG in material characterization in the future is prospected. [5][6][7] ，如生物组织内原纤维的取向检测 [8] 、 肿瘤基质胶原的检测 [9] 等；另外，各种微纳结构中 的二次谐波产生特性具有信号稳定、波长可调谐、 相干性好、超快响应性和偏振敏感性等独特优点， 作为新型微纳相干光源，在显微成像、精密探测和 非线性微纳光学器件等领域有重要的应用前景 [10][11][12][13][14][15] 。 其中，二次谐波结合共聚焦光学成像技术获得空间 光学衍射极限分辨率在二维材料晶格取向、晶界和 堆垛等结构表征方面发挥了重要作用 [16][17][18][19] ，为科研 工作者深入分析二维材料微观结构、物理性质等提 供了重要参考 [2,[20][21] 。由于二次谐波产生并不依赖 光子吸收过程，光子与材料作用时保持能量守恒， 大大避免了测试过程中对材料结构的破坏；二次谐 波测量不需要对材料进行特殊处理，可以简化实验 过程并避免外源性处理对材料结构的影响 [22] [23] ，二次谐波产生原理示意图如图 1 所示。 图 1 二次谐波产生原理示意图 [24] Fig. 1 Schematic diagram illustrating of the principle of SHG [24] 非线性介质的光学响应可以通过介质的电极化 强度 P 与入射辐射的光场强度 E 来确定，介质在外 加光电场作用下的极化强度可以表示为： P=P (1) +P (2) +P (3) +...=ε0(χ (1)…”