Direct characterization of ultraviolet-light-induced refractive index structures by scanning near-field optical microscopy

We have applied a reflection scanning near-field optical microscope to directly probe ultraviolet (UV)-light-induced refractive index structures in planar glass samples. This technique permits direct comparison between topography and refractive index changes (10/sup -5/-10/sup -3/) with submicrometer lateral resolution. The proposed method yields detailed information about the topography and index profiles of UV-written waveguides.