Zhao Zhenyu, Zhao Hui, Ako Rajour Tanyi, Zhang Jianbing, Zhao Hongwei, Sriram Sharath
Opt Express. 2019 Sep 16;27(19):26459-26470. doi: 10.1364/OE.27.026459.
Herein, we demonstrate one of the highest terahertz group delay of 42.4 ps achieved experimentally at 0.23 THz, on a flexible planar metamaterial. The unit cell of metasurface is made up of a textured closed cavity and another experimentally concentric metallic arc. By tuning the central angle of the metallic arc, its intrinsic dipolar mode is in destructive interference with the spoof localized surface plasmon (SLSP) on textured closed cavity, which results in a plasmon-induced transparency phenomenon. The measured transmittances of as-fabricated samples using terahertz-time domain spectroscopy validate numerical results using extended coupled Lorentz oscillator model. It is found that the coupling coefficient and damping ratio of SLSP relies on the radius of the ring structure of textured closed cavity. As a consequence, the slow light maximum values become manoeuverable in strength at certain frequencies of induced transparency windows. To the best of our knowledge, our experimental result is currently the highest value demonstrated so far within metasurface at terahertz band.
在此，我们展示了在柔性平面超材料上，于0.23太赫兹下通过实验实现的高达42.4皮秒的太赫兹群延迟，这是目前最高的数值之一。超表面的单元结构由一个有纹理的封闭腔体和另一个实验性的同心金属弧组成。通过调整金属弧的圆心角，其本征偶极模式与有纹理封闭腔体上的类表面等离激元（SLSP）发生相消干涉，从而导致等离激元诱导透明现象。使用太赫兹时域光谱对制备好的样品进行测量得到的透射率，验证了使用扩展耦合洛伦兹振子模型得到的数值结果。研究发现，SLSP的耦合系数和阻尼比依赖于有纹理封闭腔体环形结构的半径。因此，在诱导透明窗口的特定频率下，慢光最大值的强度变得可控。据我们所知，我们的实验结果是目前太赫兹波段超表面内展示出的最高值。
