Dagli Sahil, Shim Jiyong, Carr Delgado Hamish, Balch Halleh B, Abdollahramezani Sajjad, Chen Chih-Yi, Dolia Varun, Klopfer Elissa, Dixon Jefferson, Hu Jack, Ogunlade Babatunde, Song Jung-Hwan, Brongersma Mark L, Barton David, Dionne Jennifer A
Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA.
Department of Mechanical Engineering, Stanford University, Stanford, CA, 94305, USA.
Adv Mater. 2025 Jul 26:e06790. doi: 10.1002/adma.202506790.
Electrically tunable metasurfaces that control the amplitude and phase of light through biasing of nanoscale antennas present a route to compact modulator devices. However, most platforms face limitations in bandwidth, optical efficiency, and tuning response. Electro-optically tunable metasurfaces achieving both GHz amplitude modulation and transmissive wavefront shaping in the telecom range are presented. The resonant electro-optic nanoantenna design consists of a silicon nanobar atop thin-film lithium niobate, with gold electrodes. The nanobar is a periodically perturbed optical waveguide that supports high quality factor (Q > 1000) guided mode resonances excited with free-space light. Voltage biasing the lithium niobate tunes its refractive index, modulating the resonance of the nanobar through evanescent mode overlap. Absolute transmittance modulation of 7.1% with ±5 V applied voltage is demonstrated, and the modulation dependence on the resonance quality factor is shown. Additionally, the modulation bandwidth of these devices exceeds 800 MHz, and the electrode limitations on this bandwidth are studied. Finally, how this resonant antenna platform can enable wavefront shaping metasurfaces is shown. A beamsplitting metasurface device is demonstrated, whose diffraction efficiency can be modulated with a bandwidth of 1.03 GHz. The high-speed modulation and wavefront control capabilities of this platform provide a foundation for compact, high-bandwidth free-space communications and sensing devices.
通过对纳米级天线施加偏置来控制光的振幅和相位的电可调超表面为紧凑型调制器设备提供了一条途径。然而，大多数平台在带宽、光学效率和调谐响应方面都面临限制。本文展示了在电信频段实现GHz振幅调制和透射波前整形的电光可调超表面。共振电光纳米天线设计由位于薄膜铌酸锂顶部的硅纳米棒和金电极组成。纳米棒是一种周期性扰动的光波导，支持由自由空间光激发的高品质因数（Q>1000）的导模共振。对铌酸锂施加电压偏置会调整其折射率，通过倏逝模重叠来调制纳米棒的共振。展示了在施加±5V电压时绝对透射率调制为7.1%，并显示了调制对共振品质因数的依赖性。此外，这些器件的调制带宽超过800MHz，并研究了电极对该带宽的限制。最后，展示了这种共振天线平台如何实现波前整形超表面。展示了一种分束超表面器件，其衍射效率可在1.03GHz的带宽内进行调制。该平台的高速调制和波前控制能力为紧凑型、高带宽自由空间通信和传感设备奠定了基础。
