A Brief Review on Nonlinear Photonic Crystals Induced by Direct Femtosecond Laser Writing

Abstract

Direct femtosecond laser writing or inscription is a useful technique, and it has been 1
 employed to engineer various materials in many applications including nonlinear photonic crystals, 2
 which are of periodically patterned second-order nonlinearity to get and control the coherent light at 3
 new frequencies. By manipulation of second-order nonlinearity, either erased or poled, quasi-phase 4
 matching has been achieved in several crystals, especially three-dimensional nonlinear photonic 5
 crystals have been originally proposed and proved to be truly three-dimensional. Here we shortly 6
 review on the recent advances in the research field of nonlinear photonic crystals inscribed by 7
 femtosecond laser. We also discuss some phenomena that not understood yet and the future possible research topics in this field.