Observed Dielectric Waveguide Modes in the Visible Spectrum*

The direct images and the radiation patterns of the first few lowest-order dielectric waveguide modes were observed in the visible region of the spectrum for fibers with core and cladding indexes of refraction of 1.56 and 1.52, respectively, and for core diameters from 0.1 to 5.5 μ. The cutoff wavelengths for the observed modes are in reasonably good agreement with theory. Photographs of the modes are shown.