Surface enhanced nonlinear Cherenkov radiation in one-dimensional   nonlinear photonic crystal
  We study the configuration of efficient nonlinear Cerenkov diffraction generated from a one-dimensional nonlinear photonic crystal surface, which underlies the incorporation of both quasi-phase-matching and total internal reflection by the crystal surface. Multidirectional radiation spots with different Cerenkov angles are demonstrated experimentally, which results from different orders of reciprocal vectors. At specific angles, the incident light and total internal reflect light associating with quasi-phase-matching format completely phase-matching scheme, leading to great enhancement of harmonic efficiency. 
Xiaohui Zhao, Yuanlin Zheng, Huaijin Ren, Ning An, Xuewei Deng, and   Xianfeng Chen
physics.optics