Measurement of refractive index profiles in optical waveguides is an important issue for controlling manufacturing procedures and determination of some important characteristics of waveguides. In this paper, an optical waveguide is considered as a phase object. When collimated laser beams are illuminated on waveguides, the refractive index gradient distorts the plane waves, then the distortion is determined by use of the moire deflectometry method. Dimensions of the waveguides under study are on the order of 10 mu m, so the moire deflectometry setup was changed and optimized for measuring in the micrometer dimensions. This modified and generalized moire deflectometry technique helps to intensify plane wave distortion thousands of times and expands it to be measurable. Finally, by analysis of moire fringes, we succeeded in determining the refractive index profile of an optical waveguide by approximation of semi-cylindrical symmetry. (C) 2017 Optical Society of America
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