In order to confine waves beyond the diffraction limit, advances in fabrication techniques have enabled subwavelength structuring of matter, achieving near-field control of light and other types of waves. The price is often expensive fabrication needs and the irreversibility of device functionality, as well as the introduction of impurities, a major contributor to losses. In this Letter, we propose temporal inhomogeneities, such as a periodic drive in the electromagnetic properties of a surface which supports guided modes, as an alternative route for the coupling of propagating waves to evanescent modes across the light line, thus circumventing the need for subwavelength fabrication, and achieving the temporal counterpart of the classical Wood anomaly. We show analytically and numerically how this concept is valid for any material platform and at any frequency, and propose and model a realistic experiment in graphene to couple terahertz radiation to plasmons with unit efficiency, demonstrating that time modulation of material properties could be a tunable, lower-loss and fast-switchable alternative to the subwavelength structuring of matter for near-field wave control.

中文翻译：

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带有时间光栅的木材异常和表面波激励

为了将波限制在衍射极限之外，制造技术的进步使物质的亚波长结构成为可能，从而实现了对光和其他类型波的近场控制。价格通常是昂贵的制造需求，设备功能的不可逆性以及杂质的引入，杂质是造成损失的主要因素。在这封信中，我们提出了时间上的不均匀性，例如周期性地驱动支持导模的表面的电磁特性，作为将传播波耦合到整个光路上的e逝模的替代途径，从而避免了对亚波长的需求制作，并实现经典Wood异常的时间对应。