High efficiency second harmonic generation in one-dimensional photonic crystal coupled cavity structures

Second harmonic generation of coupled cavity structures (CCSs) fabricated in one-dimensional photonic crystals, which are composed of dispersive materials, is investigated. The fundamental wave is a localized mode, and the second harmonic wave is a traveling mode of the CCS. Using transfer matrix and effective refractive index methods, we analyze the localization and phase matching of the two modes. Using a nonlinear finite-difference time-domain method, we simulate the nonlinear process with a Gaussian pumping pulse, and both transmitted and reflected second harmonic signals are obtained. We investigate the effect of cavity number on the conversion efficiency and find the material dispersion can be compensated by the structural dispersion. For this reason, the conversion efficiency in a CCS is three orders larger than that in a bulk material of the coherence length.