  The equations for Four-Wave-Mixing in a Photonic Crystal waveguide are
derived accurately. The dispersive nature of slow-light enhancement, the impact
of Bloch mode reshaping in the nonlinear overlap integrals and the tensor
nature of the third order polarization are therefore taken into account.
Numerical calculations reveal substantial differences with simpler models,
which increase with decreasing group velocity. We predict that the gain for a
1.3 mm long, unoptimized GaInP waveguide will exceed 10 dB if the pump power
exceeds 1 W.
