Photon scanning tunneling microscope study of optical waveguides

A novel technique, photon scanning microscopy, is shown to probe directly the evanescent field outside a planar and a channel waveguide. The decay lengths for these evanescent fields were measured and correspond well to the decay lengths of the evanescent fields calculated for each structure. Two-dimensional scanning at constant intensity or constant height reveals lateral variations in these fields due to topographic changes, index of refraction inhomogeneities, or modal variations within the waveguide.