By implementing multiple sharp resonances on a single metasurface, one can combine the strong delay of constituent resonances along with the broad aggregate bandwidth of the resonance ensemble, “tricking” the delay-bandwidth limit. Ensuring that the group delay is spectrally constant across the aggregate bandwidth, we can delay arbitrarily broadband pulses without distortion. Here, we demonstrate a concrete experimental implementation of an achromatic time delay metasurface in reflection by fitting five resonant meta-atoms in a subwavelength unit cell to provide five spectrally interleaved sharp resonances (three electric and two magnetic). The proposed metasurface exploits a solely resonant phase delay, instead of propagating phase accumulation, leading to an ultrathin (λ₀/19) realization. We successfully design a group delay metasurface in the 10 GHz regime that can delay broadband, 700 MHz Gaussian pulses by 2 ns (20 times the carrier cycle). Subsequent microwave measurements verify the large (>4π) phase span over a wide high-reflection band, highlighting the practical potential of metasurfaces for dispersion control applications that rely on large and broadband phase delays.

中文翻译：

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用于宽带脉冲延迟的消色差多谐振超表面的实验实现

通过在单个超表面上实现多个尖锐共振，可以将组成共振的强延迟与共振系综的宽总带宽结合起来，“欺骗”延迟带宽限制。确保群延迟在总带宽上是频谱恒定的，我们可以延迟任意宽带脉冲而不会失真。在这里，我们通过在亚波长单位单元中安装五个共振超原子以提供五个光谱交错的尖锐共振（三个电和两个磁）来展示反射中消色差时间延迟超表面的具体实验实现。所提出的超表面利用单独的共振相位延迟，而不是传播相位累积，导致超薄（λ ₀/19) 实现。我们成功地设计了 10 GHz 范围内的群延迟超表面，可以将宽带 700 MHz 高斯脉冲延迟 2 ns（载波周期的 20 倍）。随后的微波测量验证了宽高反射带上的大 (>4π) 相位跨度，突出了超表面在依赖大和宽带相位延迟的色散控制应用中的实际潜力。