Degenerate Two-Beam Phase Conjugation in One-Dimensional ZnS–YF $_{3}$ Photonic Crystal With Central Defect Mode

This letter presents the experimental demonstration of degenerate two-beam phase conjugation (2BPC) by using a one-dimensional ZnS-YF₃ photonic crystal (PhC) with central defect mode. The effective third-order nonlinearity of the PhC sample is (2.3 ?? 0.1) ?? 10^-9 esu which is almost four orders of magnitude larger in comparison with bulk ZnS (??_ZnS ⁽³⁾ = 3.1 ?? 10^-13 esu). This large nonlinearity enhancement is attributed to the high density of mode and the electric field localization around the central defect layer near the defect mode wavelength. The realization of 2BPC utilizing defect mode in a simple PhC structure will greatly reduce the complexity to achieve compact and low-power nonlinear optical devices.