The work presents design and testing of a four-wavelength laser micro-refractometer for determination of refractive indices of liquid and solid thin films. The main goal is to achieve widening of the measured spectral region - from the violet end of the visible spectrum to the near infrared. Semiconductor lasers are used as light sources at wavelengths 406 nm, 656 nm, 910 nm and 1320 nm. Evaluation of the sample refractive index is based on critical angle determination by detection of vanishing of the diffraction pattern from a metal grating. The well known standard liquids as distillate water, ethanol, methanol, acetone and 1-bromonaphthaline are selected for approbation of the developed apparatus. The refractive indices, obtained at four wavelengths, are used to build the dispersion curves. For the purpose one-oscillatory Sellmeier's dispersion relation is chosen. Measurements at two wavelengths in the near infrared region enable more accurate description of dispersion curves. The obtained values of the refractive indices are compared to the values from other measurements made with a precise Pulfrich refractometer, in which Ar + and He-Ne lasers have been used as light sources.
