1] School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK [2] Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong.
1] Department of Physics, University of Paderborn, Warburger Straße 100 D-33098 Paderborn, Germany [2] Department of Industrial Physics and Medical Instrumentation, King Mongkut's University of Technology North Bangkok, 1518 Pibulsongkram Road, Bangkok 10800, Thailand [3] Lasers and Optics Research Group, King Mongkut's University of Technology North Bangkok, 1518 Pibulsongkram Road Bangkok 10800, Thailand.
Nat Mater. 2015 Jun;14(6):607-12. doi: 10.1038/nmat4267. Epub 2015 Apr 13.
The capability of locally engineering the nonlinear optical properties of media is crucial in nonlinear optics. Although poling is the most widely employed technique for achieving locally controlled nonlinearity, it leads only to a binary nonlinear state, which is equivalent to a discrete phase change of π in the nonlinear polarizability. Here, inspired by the concept of spin-rotation coupling, we experimentally demonstrate nonlinear metasurfaces with homogeneous linear optical properties but spatially varying effective nonlinear polarizability with continuously controllable phase. The continuous phase control over the local nonlinearity is demonstrated for second and third harmonic generation by using nonlinear metasurfaces consisting of nanoantennas of C3 and C4 rotational symmetries, respectively. The continuous phase engineering of the effective nonlinear polarizability enables complete control over the propagation of harmonic generation signals. Therefore, this method seamlessly combines the generation and manipulation of harmonic waves, paving the way for highly compact nonlinear nanophotonic devices.
在非线性光学中，能够对介质的非线性光学性质进行局部工程化至关重要。尽管极化是实现局部控制非线性的最广泛采用的技术，但它只能导致二进制非线性状态，这等效于非线性极化率中的离散π相移。在这里，受自旋-旋转耦合概念的启发，我们实验证明了具有均匀线性光学性质但具有空间变化的有效非线性极化率和连续可控相位的非线性超表面。通过使用分别由 C3 和 C4 旋转对称性的纳米天线组成的非线性超表面，证明了在二次和三次谐波产生中对局部非线性的连续相位控制。有效非线性极化率的连续相位工程使谐波产生信号的传播完全可控。因此，这种方法无缝地结合了谐波的产生和操控，为高度紧凑的非线性纳米光子器件铺平了道路。
