Xu Yadong, Wang Yang, Zhou Qingjia, Gao Lei, Fu Yangyang
Opt Lett. 2023 Aug 1;48(15):4133-4136. doi: 10.1364/OL.495263.
Here, we present a new, to the best of our knowledge, approach to control Smith-Purcell radiation (SPR) via phase-gradient metasurfaces (PGMs), i.e., periodic grating structures with gradient phase modulation. We show that the phase gradient and the parity design of the PGM can efficiently manipulate higher order diffraction to achieve perfect unidirectional SPR, which significantly alters the SPR in the spectrum and the spatial distribution beyond traditional understanding. Specifically, the even-parity PGM results in incidence-free unidirectional radiation, while the odd-parity PGM enables incidence-locking unidirectional radiation. This unidirectional SPR is very robust, ensured by the parity-dependent diffraction rule in PGMs. A modified formula is presented to reveal the relationship between the radiation wavelength and the radiation angle. Our findings offer a new way to control the electromagnetic radiation of moving charged particles (CPs) with structured materials, which may lead to novel applications in tunable, efficient light sources and particle detectors.
在此，据我们所知，我们提出了一种通过相位梯度超表面（PGM）来控制史密斯 - 珀塞尔辐射（SPR）的新方法，即具有梯度相位调制的周期性光栅结构。我们表明，PGM的相位梯度和奇偶性设计能够有效地操纵高阶衍射，以实现完美的单向SPR，这在光谱和空间分布方面显著改变了SPR，超出了传统认知。具体而言，偶奇偶性PGM导致无入射单向辐射，而奇奇偶性PGM实现入射锁定单向辐射。这种单向SPR非常稳健，由PGM中依赖奇偶性的衍射规则保证。提出了一个修正公式来揭示辐射波长与辐射角度之间的关系。我们的发现为利用结构化材料控制运动带电粒子（CP）的电磁辐射提供了一种新方法，这可能会在可调谐、高效光源和粒子探测器方面带来新的应用。
