Schlickriede Christian, Kruk Sergey S, Wang Lei, Sain Basudeb, Kivshar Yuri, Zentgraf Thomas
Department of Physics, Paderborn University, 33098 Paderborn, Germany.
Nonlinear Physics Centre, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
Nano Lett. 2020 Jun 10;20(6):4370-4376. doi: 10.1021/acs.nanolett.0c01105. Epub 2020 May 12.
Nonlinear metasurfaces incorporate many of the functionalities of their linear counterparts such as wavefront shaping, but simultaneously they perform nonlinear optical transformations. This dual functionality leads to a rather unintuitive physical behavior which is still widely unexplored for many photonic applications. The nonlinear processes render some basic principles governing the functionality of linear metasurfaces. Exemplarily, the superposition principle and the geometric optics approximation become not directly applicable to nonlinear metasurfaces. On the other hand, nonlinear metasurfaces facilitate new phenomena that are not possible in the linear regime. Here, we study the imaging of objects through a dielectric nonlinear metalens. We illuminate objects by infrared light and record their generated images at the visible third-harmonic wavelengths. We revisit the classical lens theory and suggest a for nonlinear imaging, verified both experimentally and analytically. We also demonstrate experimentally higher-order spatial correlations facilitated by the nonlinear metalens, resulting in additional image features.
非线性超表面具备许多与其线性对应物相同的功能，比如波前整形，但同时它们还能执行非线性光学变换。这种双重功能导致了一种相当不直观的物理行为，对于许多光子应用而言，这种行为仍未得到广泛探索。非线性过程使得一些支配线性超表面功能的基本原理不再适用。例如，叠加原理和几何光学近似不再直接适用于非线性超表面。另一方面，非线性超表面促成了一些在线性 regime 中不可能出现的新现象。在此，我们研究通过介电非线性金属透镜对物体进行成像。我们用红外光照射物体，并在可见的三次谐波波长处记录它们生成的图像。我们重新审视经典透镜理论，并提出一种用于非线性成像的方法，该方法已通过实验和分析得到验证。我们还通过实验证明了非线性金属透镜促成的高阶空间相关性，从而产生了额外的图像特征。
