Beijing Center for Crystal Research and Development, Key Lab of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Molecules. 2023 Jan 22;28(3):1116. doi: 10.3390/molecules28031116.
The accurate evaluation of nonlinear optical (NLO) coefficient, the main parameter affecting light conversion efficiency, plays a crucial role in the development of NLO materials. The Kurtz-Perry powder technique can evaluate second-harmonic generation (SHG) intensity in pristine powder form, saving a significant amount of time and energy in the preliminary screening of materials. However, the Kurtz-Perry method has recently been subject to some controversy due to the limitations of the Kurtz-Perry theory and the oversimplified experimental operation. Therefore, it is very meaningful to revisit and develop the Kurtz-Perry technique. In this work, on the basis of introducing the light scattering effect into the original Kurtz-Perry theory, the theoretical expression of second-harmonic generation intensity with respect to band gap and refractive index are analyzed. In addition, the reference-dependent SHG measurements were carried out on polycrystalline LiBO (LBO), AgGaQ (Q = S, Se), BaGaQ (Q = S, Se), and ZnGeP (ZGP), and the results of SHG response emphasize the importance of using appropriate references to the Kurtz-Perry method. In order to obtain reliable values of nonlinear coefficients, two criteria for selecting a reference compound were proposed: (1) it should possess a band gap close to that of the sample to be measured and (2) it should possess a refractive index close to that of the sample to be measured. This work might shed light on improvements in accuracy that can be made for effective NLO coefficients obtained using the Kurtz-Perry method.
非线性光学（NLO）系数的准确评估是影响光转换效率的主要参数，在 NLO 材料的发展中起着至关重要的作用。Kurtz-Perry 粉末技术可以在原始粉末形式下评估二次谐波产生（SHG）强度，从而在材料的初步筛选中节省大量的时间和精力。然而，由于 Kurtz-Perry 理论的局限性和过于简化的实验操作，Kurtz-Perry 方法最近受到了一些争议。因此，重新审视和发展 Kurtz-Perry 技术是非常有意义的。在这项工作中，在将光散射效应引入原始 Kurtz-Perry 理论的基础上，分析了二次谐波产生强度与能带隙和折射率的理论表达式。此外，还对多晶 LiBO（LBO）、AgGaQ（Q=S，Se）、BaGaQ（Q=S，Se）和 ZnGeP（ZGP）进行了参考依赖性 SHG 测量，SHG 响应的结果强调了使用适当的参考物对 Kurtz-Perry 方法的重要性。为了获得可靠的非线性系数值，提出了选择参考化合物的两个标准：（1）它应具有与待测样品相近的能带隙，（2）它应具有与待测样品相近的折射率。这项工作可能为使用 Kurtz-Perry 方法获得有效 NLO 系数的准确性改进提供一些启示。
