We propose a new method of measuring both the nonlinear refractive index and the nonlinear absorption coefficient using transmission spectum for the first time.We show theoretically that the two parameters can be obtained from the linear and nonlinear transmission spectra of the medium and the distribution function of the dye laser frequency.The method requires very simple experimental apparatus.The nonlinear refractive indices and the nonlinear absorption coefficient and their sign can be obtained from the experimental results in the relatively large wavelength range.We can get two wavelengths at the nonlinear refraction and absorption maximums.We have obtained both thenonlinear refractive index and the nonlinear absorption coefficient as a function of the wavelength for ZnSe-ZnS multiple quantum wells on transparent CaF

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substrate at 77K.