Third-harmonic generation in silicon photonic crystals and microcavities

Abstract

Third-harmonic generation (THG) is observed in photonic crystals and microcavities formed from porous silicon. The THG spectra reveal an intensity enhancement at the photonic band gap edge of these photonic crystals and at the resonance of the fundamental radiation with the microcavity mode. The enhancement is related to the combination of the phase matching and fundamental light localization. The amplitudes of the THG peaks are strongly affected by the competition between the porous silicon absorption at the third-harmonic wavelength and the three-photon resonance of cubic susceptibility of silicon achieved in the vicinity of the ${E}_{0}^{\ensuremath{'}}∕{E}_{1}$ critical point.