Extended blue supercontinuum generation in cascaded holey fibers

By combining multiple photonic crystal fibers with sequentially decreasing zero-dispersion wavelengths we have produced a 1.2 W average-power white-light continuum, covering the visible-near-infrared spectrum from 0.44 to 1.89 microm (10 dB width), with an all-fiber picosecond ytterbium pump laser. Wavelengths as short as the ultraviolet (0.35 microm), and spectral power densities of more than 2 mW/nm in the blue spectral region, have been generated. The process is understood in terms of optimizing four-wave mixing phase matching to enhance short-wavelength generation.