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

The refractive index profile of a straight channel phosphosilicate glass planar optical waveguide is obtained with high spatial resolution (approximately 0.25 micrometers ) using near- field scanning optical microscopy (NSOM). The optical intensity profile of the waveguide mode is measured by NSOM and the refractive index distribution is calculated from the measured intensity. The calculated refractive index distribution is in agreement with that expected from the fabrication procedure and provides evidence for phosphorous diffusion between the core and cladding regions.