发表机构
Korea Advanced Institute of Science and Technology; California Institute of Technology（韩国科学技术院; 加州理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出一种基于锗米氏谐振器与石墨烯条带集成的有源透射超表面，通过静电门控和热光效应实现独立振幅与相位调制，在红外波段达到约100%透射率调制和282°相位调制，并演示了衍射效率超90%的光束偏转。
AI 中文摘要
有源超表面是空间光调制器（SLM）在诸如全息术、光束整形和光探测与测距（LiDAR）等应用中的一种有前景的平台，因为它们能够在亚波长尺度上对光的振幅和相位进行动态控制。其中，透射型超表面为传统空间光调制器提供了一种紧凑的替代方案，因为它们允许与芯片级光源进行单片集成。虽然先前已在有源反射型超表面中演示了独立的振幅和相位调制，但由于设计有源透射型超表面固有的挑战，这一重要里程碑尚未在透射中实现。在此，我们从理论上演示了一种有源透射超表面，它能够在红外波段实现独立的振幅和相位调制。所提出的超表面由与石墨烯条带集成的高品质因子长方体锗（Ge）米氏谐振器组成。利用石墨烯的带内和带间跃迁，静电门控能够在同一器件中于一个光谱频率处将透射率从接近0%调制到5%，并在另一个频率处实现281°的纯相位调制。为了在同一工作波长下实现两种类型的调制，我们使用锗的热光效应作为全局调谐机制来光谱对准谐振频率，从而在不同基础温度下实现透射率和纯相位调制。所提出的双机制架构实现了约100%的透射率调制效率和282°的纯相位调制。最后，我们通过单独寻址每个单元来演示纯相位调制的有效性，实现了一个相对衍射效率超过90%的光束偏转器件。我们可单独寻址的有源超表面为紧凑、动态可重构的超光子器件开辟了一条道路。
英文摘要
Active metasurfaces are a promising platform for spatial light modulators (SLMs) in applications such as holography, beam shaping, and light detection and ranging (LiDAR), as they enable dynamic control over the amplitude and phase of light at subwavelength scales. Among these, transmissive metasurfaces offer a compact alternative to conventional SLMs, since they allow monolithic integration with chip-scale light sources. While independent amplitude and phase modulation have been previously demonstrated in active reflective metasurfaces, this important milestone has not been achieved in transmission due to the inherent challenges in designing active transmissive metasurfaces. Here, we theoretically demonstrate an active transmissive metasurface that enables independent amplitude and phase modulation in the mid-infrared. The proposed metasurface consists of high-Q cuboid germanium (Ge) Mie resonators integrated with graphene stripes. Utilizing the intraband and interband transitions of graphene, electrostatic gating enables modulation of the transmittance from near 0% to 5% at one spectral frequency and achieves 281° phase-only modulation at another frequency in the same device. To achieve both types of modulation at the same operating wavelength, we use the thermo-optic effect of Ge as a global tuning mechanism to spectrally align the resonant frequencies, enabling both transmittance and phase-only modulation at different base temperatures. The proposed dual-mechanism architecture achieves transmittance modulation efficiency of ~100% and 282° phase-only modulation. Finally, we demonstrate the efficacy of phase-only modulation by individually addressing each unit cell to realize a beam-steering device with relative diffraction efficiencies over 90%. Our individually addressable active metasurface opens a route toward compact, dynamically reconfigurable metaphotonic devices.
Comments56 pages, 5 figures, 18 supplementary figures
