Wang Hsiang-Chu, Achouri Karim, Martin Olivier J F
Nanophotonics and Metrology Laboratory, Swiss Federal Institute of Technology Lausanne (EPFL), 1015 Lausanne, Switzerland.
ACS Photonics. 2022 Jul 20;9(7):2438-2447. doi: 10.1021/acsphotonics.2c00563. Epub 2022 Jun 28.
Optical metasurfaces rely on subwavelength scale nanostructures, which puts significant constraints on nanofabrication accuracies. These constraints are becoming increasingly important, as metasurfaces are maturing toward real applications that require the fabrication of very large area samples. Here, we focus on beam steering gradient metasurfaces and show that perfect nanofabrication does not necessarily equate with best performances: metasurfaces with missing elements can actually be more efficient than intact metasurfaces. Both plasmonic metasurfaces in reflection and dielectric metasurfaces in transmission are investigated. These findings are substantiated by experiments on purposely misfabricated metasurfaces and full-wave calculations. A very efficient quasi-analytical model is also introduced for the design and simulations of metasurfaces; it agrees very well with full-wave calculations. Our findings indicate that the substrate properties play a key role in the robustness of a metasurface and the smoothness of the approximated phase gradient controls the device efficiency.
光学超表面依赖于亚波长尺度的纳米结构，这对纳米制造精度提出了重大限制。随着超表面朝着需要制造非常大面积样品的实际应用方向发展，这些限制变得越来越重要。在这里，我们专注于光束转向梯度超表面，并表明完美的纳米制造并不一定等同于最佳性能：具有缺失元件的超表面实际上可能比完整的超表面更高效。我们研究了反射型等离子体超表面和透射型介质超表面。通过对故意制造错误的超表面进行实验和全波计算，证实了这些发现。还引入了一个非常有效的准解析模型用于超表面的设计和模拟；它与全波计算非常吻合。我们的研究结果表明，衬底特性在超表面的稳健性中起关键作用，并且近似相位梯度的平滑度控制着器件效率。
