Spectroscopy of second- and third-harmonic generation in silicon photonic crystals and microcavities

In this paper enhanced second- and third-harmonic generation (SHG and THG) is observed in one-dimensional photonic crystals and microcavities (MCs) formed from mesoporous silicon. The SHG and THG spectra measured in both frequency and wave-vector domains reveal two types of the resonant enhancement, namely, as the fundamental radiation is tuned across the photonic band gap edge and if it is in the resonance with the MC mode. The SHG and THG enhancements are observed also in coupled photonic-crystal microcavities, in which the electromagnetic interaction between coupling cavity spacers is controlled by the intermediate Bragg reflector. The eigenmodes of coupled MCs are split with spectral (angular) gap determined by the intermediate photonic crystal transmittance.