A light beam’s frequency can blueshift when the beam travels through a medium that exhibits a time-dependent decrease in the refractive index. Here we show that a metasurface made of a plasmonic antenna array on a thin indium tin oxide (ITO), which exhibits epsilon-near-zero (ENZ) response, can behave as a time-varying medium and change the frequency of a sufficiently strong light beam through self-action effect. Specifically, we observe that a near-resonant optical excitation of the 92 nm thick metasurface leads to an intensity-dependent blueshift of the excitation pulse. We measured a maximum blueshift of ∼1.6 THz with ∼4 GW/cm² incident intensity. The observed effect using an ITO-based ENZ metasurface has an energy requirement that is up to 200× lower than implementations using ITO alone.

中文翻译：

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使用随时间变化的近零零元超颖表面的光子加速

当光束穿过介质时，其频率会发生蓝移，该介质表现出随时间而变的折射率降低。在这里，我们显示了由等离子天线阵列在薄的铟锡氧化物（ITO）上形成的超表面，其表现出ε接近零（ENZ）的响应，可以充当随时间变化的介质并改变足够强的频率光束通过自作用效应。具体来说，我们观察到92 nm厚超颖表面的近共振光学激发导致激发脉冲的强度依赖性蓝移。我们测得的最大蓝移约为1.6 THz，入射强度约为4 GW / cm ²。与仅使用ITO的实现相比，使用基于ITO的ENZ超表面所观察到的效果所需要的能量要低200倍。