Spectral domain Z-scan technique

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.