Refractive index profiling of optical waveguides using near-field scanning optical microscopy

We present a method in which we take advantage of the high spatial resolution and experimental simplicity afforded by near-field scanning optical microscopy (NSOM) to determine the refractive index profiles of optical waveguides. We use NSOM to measure the near-field intensities of the guided modes in planar waveguides and optical fibers and calculate numerically, from the measured intensities, the refractive index distributions.