Abstract-Demonstration of group delay above 40 ps at terahertz plasmon-induced transparency windows

Zhenyu Zhao, Hui Zhao, Rajour Tanyi Ako, Jianbing Zhang, Hongwei Zhao, and Sharath Sriram

. (a) Schematic diagram of a unit cell of proposed binary MM, in which p = 420 µm, r = 90 µm, w = 4 µm, h = 60 µm, g = 15 µm, respectively. l is the length of the metallic arc. (b) Microscopic images (VHX-500, Keyence Inc.) of unit cell of as-fabricated binary MM. (c) A schematic diagram showing terahertz transmission and group velocity delay through a periodic array of binary MM, as measured using a THz-TDS. KTHz refers to the wave vector of incident THz pulse. EX and HY refer to the electrical and magnetic component of the incident electromagnetic waves, respectively. XYZ are the coordinate axis in free space.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-19-26459

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.

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