Zagaglia Luca, Demontis Valeria, Rossella Francesco, Floris Francesco
Tyndall National Institute, University College Cork, Cork, Ireland.
NEST Laboratory, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Pisa, Italy.
Nanotechnology. 2021 May 25;32(33). doi: 10.1088/1361-6528/abff8b.
Recent advances in the nanofabrication and modeling of metasurfaces have shown the potential of these systems in providing unprecedented control over light-matter interactions at the nanoscale, enabling immediate and tangible improvement of features and specifications of photonic devices that are becoming always more crucial in enhancing everyday life quality. In this work, we theoretically demonstrate that metasurfaces made of periodic and non-periodic deterministic assemblies of vertically aligned semiconductor nanowires can be engineered to display a tailored effective optical response and provide a suitable route to realize advanced systems with controlled photonic properties particularly interesting for sensing applications. The metasurfaces investigated in this paper correspond to nanowire arrays that can be experimentally realized exploiting nanolithography and bottom-up nanowire growth methods: the combination of these techniques allow to finely control the position and the physical properties of each individual nanowire in complex arrays. By resorting to numerical simulations, we address the near- and far-field behavior of a nanowire ensemble and we show that the controlled design and arrangement of the nanowires on the substrate may introduce unprecedented oscillations of light reflectance, yielding a metasurface which displays an electromagnetic behavior with great potential for sensing. Finite-difference time-domain numerical simulations are carried out to tailor the nanostructure parameters and systematically engineer the optical response in the VIS-NIR spectral range. By exploiting our computational-methods we set-up a complete procedure to design and test metasurfaces able to behave as functional sensors. These results are especially encouraging in the perspective of developing arrays of epitaxially grown semiconductor nanowires, where the suggested design can be easily implemented during the nanostructure growth, opening the way to fully engineered nanowire-based optical metamaterials.
超表面的纳米制造和建模方面的最新进展表明，这些系统有潜力在纳米尺度上对光与物质的相互作用提供前所未有的控制，从而能够直接且切实地改善光子器件的特性和规格，而这些特性和规格对于提升日常生活质量正变得越来越关键。在这项工作中，我们从理论上证明，由垂直排列的半导体纳米线的周期性和非周期性确定性组件构成的超表面可以被设计成展现出定制的有效光学响应，并提供一条合适的途径来实现具有可控光子特性的先进系统，这对于传感应用尤其有趣。本文所研究的超表面对应于可以通过纳米光刻和自下而上的纳米线生长方法在实验上实现的纳米线阵列：这些技术的结合能够精细地控制复杂阵列中每根纳米线的位置和物理性质。通过数值模拟，我们研究了纳米线集合的近场和远场行为，并表明在衬底上对纳米线进行可控的设计和排列可能会引入前所未有的光反射振荡，从而产生一种具有巨大传感潜力的电磁行为的超表面。我们进行了时域有限差分数值模拟，以调整纳米结构参数并系统地设计可见光 - 近红外光谱范围内的光学响应。通过利用我们的计算方法，我们建立了一个完整的程序来设计和测试能够作为功能传感器的超表面。从开发外延生长的半导体纳米线阵列的角度来看，这些结果尤其令人鼓舞，因为所建议的设计可以在纳米结构生长过程中轻松实现，为完全工程化的基于纳米线的光学超材料开辟了道路。
