Reconfigurable metalenses are compact optical components composed by arrays of meta-atoms that offer unique opportunities for advanced optical systems, from microscopy to augmented reality platforms. Although poorly explored in the context of reconfigurable metalenses, thermo-optical effects in resonant silicon nanoresonators have recently emerged as a viable strategy to realize tunable meta-atoms. In this work, we report the proof-of-concept design of an ultrathin (300 nm thick) and thermo-optically reconfigurable silicon metalens operating at a fixed, visible wavelength (632 nm). Importantly, we demonstrate continuous, linear modulation of the focal-length up to 21% (from 165 μm at 20 °C to 135 μm at 260 °C). Operating under right-circularly polarized light, our metalens exhibits an average conversion efficiency of 26%, close to mechanically modulated devices, and has a diffraction-limited performance. Overall, we envision that, combined with machine-learning algorithms for further optimization of the meta-atoms, thermally reconfigurable metalenses with improved performance will be possible. Also, the generality of this approach could offer inspiration for the realization of active metasurfaces with other emerging materials within field of thermo-nanophotonics.

中文翻译：

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热重构元透镜

可重构超透镜是由元原子阵列组成的紧凑型光学组件，为从显微镜到增强现实平台的先进光学系统提供了独特的机会。尽管在可重构超透镜的背景下探索得很少，但谐振硅纳米谐振器中的热光效应最近已成为实现可调元原子的可行策略。在这项工作中，我们报告了在固定可见波长（632 nm）下工作的超薄（300 nm 厚）和热光可重构硅元透镜的概念验证设计。重要的是，我们展示了高达 21% 的焦距的连续线性调制（从 20 °C 时的 165 μm 到 260 °C 时的 135 μm）。在右圆偏振光下运行，我们的超透镜表现出 26% 的平均转换效率，接近机械调制设备，并具有衍射极限性能。总体而言，我们设想，结合机器学习算法以进一步优化元原子，具有改进性能的热可重构超透镜将成为可能。此外，这种方法的普遍性可以为用热纳米光子学领域的其他新兴材料实现有源超表面提供灵感。