  We demonstrate second harmonic generation in photonic crystal cavities in
(001) and (111)B oriented GaAs. The fundamental resonance is at 1800 nm,
leading to second harmonic below the GaAs bandgap. Below-bandgap operation
minimizes absorption of the second harmonic and two photon absorption of the
pump. Photonic crystal cavities were fabricated in both orientations at various
in-plane rotations of the GaAs substrate. The rotation dependence and farfield
patterns of the second harmonic match simulation. We observe similar maximum
efficiencies of 1.2 %/W in (001) and (111)B oriented GaAs.
