Optical phase conjugation in third-order nonlinear photonic crystals

We predict that the efficiency of the optical phase conjugation generation can be enhanced by more than four orders of magnitude in a ${\chi }^{\left(3\right)}$ nonlinear superlattice, as compared with that in a homogeneous nonlinear medium of the same sample thickness and ${\chi }^{\left(3\right)}$ nonlinearity. Such an effective enhancement utilizes the localized properties of the fields inside the sample at the band-edge state, gap-soliton state, or defect state. Due to the presence of feedback mechanism at each interface of a superlattice, we also predict that the phase conjugation can still be effectively generated when only one pump wave is used.