Characterizing the nonlinear optical properties of various materials plays a prerequisite role in nonlinear optics. Among different measurement methods, the well-known Z-scan technique and the modified versions have been recognized as simple and accurate methods for measuring both the real and imaginary parts of the nonlinear refractive index. However, the Z-scan methods based on detecting small beam variations impose a severe restriction on the roughness of materials. Therefore, measuring nonlinear optical properties of highly scattering media still remain challenging. Inspired by the innovation of the conventional Z-scan method that replaces the measurement of the wavefront phase shift by measuring the spatial pattern in the far-field, the spectral domain Z-scan technique is presented in this paper. It has the great potential in characterizing the nonlinear refractive index of highly scattering medium, since the scattering efficiency is insensitive to the wavelength for Mie scattering, which occurs for wavelengths far smaller than the roughness. Moreover, to demonstrate the advantages of the spectral domain Z-scan technique, the nonlinear refractions of polished slides and frosted slides were measured, which agree well with previous reports.

表征各种材料的非线性光学特性在非线性光学中起着先决条件。在不同的测量方法中，众所周知的Z扫描技术和改进版本已被公认为是用于测量非线性折射率的实部和虚部的简单而准确的方法。然而，基于检测小光束变化的 Z 扫描方法对材料的粗糙度施加了严格的限制。因此，测量高散射介质的非线性光学特性仍然具有挑战性。受到传统Z扫描方法创新的启发，该方法通过测量远场中的空间模式来代替波前相移的测量，本文提出了一种谱域Z扫描技术。它在表征高散射介质的非线性折射率方面具有巨大的潜力，因为散射效率对米氏散射的波长不敏感，米氏散射发生的波长远小于粗糙度。此外，为了展示谱域 Z 扫描技术的优势，测量了抛光幻灯片和磨砂幻灯片的非线性折射，这与之前的报告非常吻合。