ENDLESSLY SINGLE-MODE PHOTONIC CRYSTAL FIBER

We made an all-silica optical fiber by embedding a central core in a t wo-dimensional photonic crystal with a micrometer-spaced hexagonal arr ay of air holes. An effective-index model confirms that such a fiber c an be single mode for any wavelength. Its useful single-mode range wit hin the transparency window of silica, although wide, is ultimately bo unded by a bend-loss edge at short wavelengths as well as at long wave lengths. (C) 1997 Optical Society of America.