Second-order nonlinear mixing in planar photonic crystal microcavities
  Second-harmonic and sum-frequency mixing phenomena associated with 3D-localized photonic modes are studied in InP-based planar photonic crystal microcavities excited by short-pulse radiation near 1550 nm. Three-missing-hole microcavities that support two closely-spaced modes exhibit rich second-order scattering spectra that reflect intra- and inter-mode mixing via the bulk InP chi(2) during ring-down after excitation by the broadband, resonant pulse. Simultaneous excitation with a non-resonant source results in tunable second-order radiation from the microcavity. 
Murray W. McCutcheon, Georg W. Rieger, Jeff F. Young, Dan Dalacu,   Simon Frederick, Philip J. Poole, and Robin L. Williams