  We report a 1 um continuous wave pumped supercontinuum which extends short of
the pump wavelength to 0.65 um. This is achieved by using a 50 W Yb fibre laser
in combination with a photonic crystal fibre with a carefully engineered zero
dispersion wavelength. We show that the short wavelength generation is due to a
combination of four-wave mixing and dispersive wave trapping by solitons. The
evolution and limiting factors of the continuum are discussed.
