Abstract
Consideration is given to the possibilities of measuring the refractive index n of dielectric samples by means of spontaneous gratings produced by an s‐polarized laser beam in a photosensitive thin film applied to a sample in vacuum. With the specific choice of the film thickness, the value of n is determined from diffraction measurements of the period of a spontaneous grating with the error Δn = ±0.002. The method allows measurement of n isotropic and anisotropic samples within the range 1.32.5 on plane and cylindrical surfaces with the area determined by the section of the laser beam that induces the spontaneous grating. Examples of measurements of n on plane surfaces of glasses, a LiNbO3 crystal, and on the cylindrical surface of a ruby rod are presented.