Dynamic optical metasurfaces with ultrafast temporal response, i.e., spatiotemporal optical metasurfaces, provide attractive solutions and open fascinating perspectives for modern highly integrated optics and photonics. In this work, electro-optically controlled optical metasurfaces operating in reflection and utilizing resonant waveguide mode excitation are demonstrated from the viewpoint of free-space propagating light modulation. The modulation of reflected light power with superior characteristics in comparison with prior research is achieved by identifying a suitable low-loss waveguide mode and exploiting its resonant excitation. The electro-optic Pockels effect in a 300 nm-thick lithium niobate (LN) film sandwiched between a continuous thick gold film and an array of gold nanostripes, serving also as control electrodes, is exploited to realize fast and efficient light modulation. The fabricated compact (active area <1000 µm2) modulators operate in the wavelength range of 850–950 nm, featuring a maximum intensity modulation depth of 42 % at the driving voltage of ±10 V within the bandwidth of 13.5 MHz (with the potential bandwidth of 6.5 GHz). The introduced nonlocal electro-optic metasurface configuration opens new avenues towards the realization of ultrafast, efficient, and robust free-space light modulators based on an LN flat optics approach.

中文翻译：

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用于自由空间光调制的非局域电光超表面

具有超快时间响应的动态光学超表面，即时空光学超表面，为现代高度集成的光学和光子学提供了有吸引力的解决方案和开辟了迷人的前景。在这项工作中，从自由空间传播光调制的角度展示了以反射方式运行并利用谐振波导模式激发的电光控制光学超表面。通过识别合适的低损耗波导模式并利用其共振激发，实现​​了与先前研究相比具有优异特性的反射光功率调制。300 nm 厚的铌酸锂 (LN) 薄膜中的电光 Pockels 效应夹在连续的厚金薄膜和金纳米条纹阵列之间，也用作控制电极，被用来实现快速高效的光调制。制造的紧凑型（活性区域 <1000 µm2个) 调制器在 850-950 nm 的波长范围内工作，在 13.5 MHz 的带宽（潜在带宽为 6.5 GHz）内，在 ±10 V 的驱动电压下具有 42% 的最大强度调制深度。引入的非局部电光超表面配置为实现基于 LN 平面光学方法的超快、高效和稳健的自由空间光调制器开辟了新途径。