(a) Contour plot of the recorded near-field pattern of the guided mode superimposed upon an approximately scaled portion of a scanning electron micrograph to show the relative orientation of the modal field pattern and the fiber microstructure. The field is strongly peaked in the center, and there is a factor-of-25 difference between the innermost (strongest) and the outermost intensity contours. (b) Calculated Fourier transform of the pattern, again strongly peaked in the center.
(a) Photographed far-field pattern at 632.8 nm. (b) Same as in
(a) but with the central part of the field overexposed to show the higher-order spots on the fringes of the pattern, which demonstrate the integrity of the periodic structure.