To distinctively identify two objects at the deep-subwavelength scales requires sharp superfocusing to overcome the diffraction limit. However, conventional superfocusing effect and information-carrying capacity are limited by the focal length and single focusing field (only electric or magnetic field), which are hard to be apparently improved. Here, we introduce the concept of “dual-foci superfocusing”, an advanced focusing form that can provide either one or two focusing spots, simultaneously converging both electric and magnetic fields and presenting an effect of electromagnetostatic space-division multiplexing. The physical mechanism of the dual-foci superfocusing is analyzed and synthesized by an original theory of shaping functional fields using hybrid-magnitude evanescent modes. Through a terahertz plasmonic array, the dual-foci superfocusing is numerically demonstrated, whose metric (ratio of focal length to focusing-spot size) is sufficiently improved from traditional 1–1.8 up to 2.8. The proposed methodology could be exploited as a platform to investigate the novel concurrent characteristics of superfocusing and might represent an important step toward the development of beam manipulation and sophisticated holography.

中文翻译：

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广义波前处理：具有混合幅度渐逝模式和太赫兹空分复用的双焦点超聚焦

为了在深亚波长尺度上区分两个物体，需要锐利的超聚焦来克服衍射极限。然而，传统的超聚焦效果和信息承载能力受到焦距和单聚焦场（只有电场或磁场）的限制，难以得到明显改善。在这里，我们引入了“双焦点超聚焦”的概念，这是一种先进的聚焦形式，可以提供一个或两个聚焦点，同时会聚电场和磁场，并呈现出电磁静空分复用的效果。通过使用混合幅度渐逝模式塑造功能场的原始理论，分析和综合了双焦点超聚焦的物理机制。通过太赫兹等离子体阵列，数值证明了双焦点超聚焦，其度量（焦距与聚焦光斑尺寸的比率）从传统的 1-1.8 提高到 2.8。所提出的方法可以用作研究超聚焦的新并发特性的平台，并且可能代表朝着光束操纵和复杂全息技术发展迈出的重要一步。