Abstract-Broadband terahertz rotator with an all-dielectric metasurface

Quanlong Yang, Xieyu Chen, Quan Xu, Chunxiu Tian, Yuehong Xu, Longqing Cong, Xueqian Zhang, Yanfeng Li, Caihong Zhang, Xixiang Zhang, Jiaguang Han, and Weili Zhang

Fig. 1. (a) Conceptual description of the metasurface based on two identical dielectric antennas to manipulate the polarization of the terahertz wave. 𝛼$\alpha$ and 𝛽$\beta$ represent the orientations of two dielectric antennas (marked by the orange arrows), and 𝛾$\gamma$ is the effective optical axis orientation from the superposition of two antennas (marked by the navy arrow). (b) Schematic illustration of the two silicon antennas with geometrical parameters 𝑊=45  μm$W=45\mathrm{\mu m}$, 𝐿=180  μm$L=180\mathrm{\mu m}$, 𝐻=200  μm$H=200\mathrm{\mu m}$, and period 𝑃=375  μm$P=375\mathrm{\mu m}$. (c),(d) Schematic diagrams for high-quality polarization generation. Without introducing the phase gradient, both the 𝑥$x$-polarized and 𝑦$y$-polarized light propagates in the normal direction forming dispersive polarization states within the frequency range of interest. The phase gradient enables spatial separation of the two orthogonal polarization components, giving rise to pure linearly polarized components within a broad frequency range.

https://www.osapublishing.org/prj/fulltext.cfm?uri=prj-6-11-1056&id=399205

Polarization manipulation is essential in developing cutting-edge photonic devices ranging from optical communication displays to solar energy harvesting. Most previous works for efficient polarization control cannot avoid utilizing metallic components that inevitably suffer from large ohmic loss and thus low operational efficiency. Replacing metallic components with Mie resonance-based dielectric resonators will largely suppress the ohmic loss toward high-efficiency metamaterial devices. Here, we propose an efficient approach for broadband, high-quality polarization rotation operating in transmission mode with all-dielectric metamaterials in the terahertz regime. By separating the orthogonal polarization components in space, we obtain rotated output waves with a conversion efficiency of 67.5%. The proposed polarization manipulation strategy shows impressive robustness and flexibility in designing metadevices of both linear- and circular-polarization incidences.

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