We report on the observation of Čerenkov emission of a third-harmonic frequency in a
two-dimensional nonlinear photonic crystal, where the second-order nonlinearity chi((2)) is spatially modulated by the reversal of ferroelectric domains. We analyze both spatial and polarization properties of the emitted radiation and find the results in agreement with our theoretical predictions.
Sheng, Y. [et al.]. Cerenkov third-harmonic generation in chi((2)) nonlinear photonic crystal. "Applied physics letters", 13 Juny 2011, vol. 98, núm. 24, p. 241114-1-241114-3.