Resonant second-harmonic generation and mode dispersion in photonic crystal waveguides

Linear and nonlinear optical measurements on GaAs/AlGaAs photonic crystal waveguides with square lattice are reported. Second-harmonic generation in reflection shows a resonant enhancement when the pump beam is frequency- and momentum-matched to a photonic mode in the slab. A full three-dimensional theory of waveguide-embedded photonic crystals allows to determine the dispersion of photonic modes and the intrinsic radiative losses of quasi-guided modes lying above the light line.