  We consider an index-guiding silica photonic crystal fiber with a triangular
air-hole structure and a poled quadratic nonlinearity. By tuning the pitch and
the relative hole size, second-harmonic generation with zero group-velocity
mismatch is found for any fundamental wavelength above 780 nm. The
phase-velocity mismatch has a lower limit with coherence lengths in the micron
range. The dimensionless nonlinear parameter is inversely proportional to the
pitch and proportional to the relative hole size. Selected cases show
bandwidths suitable for 20 fs pulse-conversion with conversion efficiencies as
high as 25%/mW.
