Nonlinear Optics: Semi‐Nonlinear Nanophotonic Waveguides for Highly Efficient Second‐Harmonic Generation (Laser Photonics Rev. 13(3)/2019)

In article number 1800288 , Rui Luo and co‐workers propose a universal design principle to enhance optical parametric generation. By heterogeneous integration of linear and nonlinear materials in the core of a nanophotonic waveguide, the spatial symmetry of the optical nonlinearity can be broken to optimize the mode overlap factor in modal‐phase‐matched second‐harmonic generation, resulting in a dramatically improved conversion efficiency. This approach promises energy efficient photonic signal processing on a variety of integrated platforms.