As the nonlinear refractive index ([Formula: see text]) of human cancerous skin tissues is an important parameter in characterizing the optical response in laser–tissue interaction, the interferometry method was applied for early diagnosis. Simple method of interferometry measurement has been applied to measure the tissues’ [Formula: see text] in vitro from cancerous human skin samples (BCC and SCCs) in three thicknesses. Also, to compare the sensitivity and accuracy of the interferometry method, the [Formula: see text]-scan method was used. The results show that in comparison with healthy skin tissue, the cancerous skin has nonlinear response and this index increases with the thickness of samples.

In this paper, for the first time, we introduce a simple way for finding the nonlinear optical properties of nanoparticles. The Michelson interferometer was used for calculating nonlinear refractive index. In comparison with conventional methods, the interferometry has high sensitivity and uses a single coherent beam that reduces the complexity and cost of experimental setup. The He-Ne laser with 75 mW laser irradiation at 632.8 nm was applied to different concentrations of TiO2 nanoparticles as a notable sample. By analysing the changes at interferometric patterns of different samples, the magnitude of (n2) was obtained in 10 −8 cm 2 /W order. To confirm the interferometry results, the common Z-scan method was used to measure the nonlinear refractive index which reveals that the results are in good agreement with the interferometry method.