where n0=1.37 represents the linear refractive index of ethanol, n_2 is the non-linear refractive index of TaSe2 and I is the incident intensity of the laser beam. Using different light wavelengths, in particular λ=532 nm and λ=671 nm, it is possible to measure both n_2 and \chi^{(3)}, the third order nonlinear susceptibility.
