Anomalous dispersion in photonic crystal fiber

We describe the measured group-velocity dispersion characteristics of sever al air-silica photonic crystal fibers with anomalous group-velocity dispers ion at visible and near-infrared wavelengths. The values measured over a br oad spectral range are compared to those predicted for an isolated strand o f silica surrounded by air. We demonstrate a strictly single-mode fiber whi ch has zero dispersion at a wavelength of 700 nm, These fibers are signific ant for the generation of solitons and supercontinua using ultrashort pulse sources.