Opt Lett. 2021 Sep 1;46(17):4164-4167. doi: 10.1364/OL.431285.
Polarization conversion is useful for studies of chiral structures in biology and chemistry, and for polarization diversity in communications. It is conventionally realized with wave plates, which, however, present challenges due to limited material availability, as well as narrow bandwidth and low efficiency at terahertz frequencies. To enhance bandwidth and efficiency, the concept of the Huygens' metasurface is adopted here for a transmissive half-wave plate. The half-wave metasurface is designed following the optimal frequency-independent circuit parameters provided by a broadband semi-analytical approach. Simulation results of an optimal design suggest that a 15-dB extinction ratio can be sustained from 219 GHz to 334 GHz, corresponding to a fractional bandwidth of 41.6%. The measured results indicate that the fabricated structure enables a 15-dB extinction ratio from 220 GHz to 303 GHz, with a cross-polarization transmission efficiency above 76.7% for both linear and circular polarizations. This half-wave metasurface design can be readily integrated into compact terahertz systems for diverse applications.
偏振转换在生物和化学中的手性结构研究以及通信中的偏振分集中很有用。它通常通过波片来实现，然而，由于材料可用性有限，以及在太赫兹频率下带宽窄和效率低，波片会带来挑战。为了提高带宽和效率，这里采用了惠更斯超表面的概念来设计透射式半波片。半波超表面的设计遵循宽带半解析方法提供的最优频率无关电路参数。优化设计的模拟结果表明，从 219GHz 到 334GHz 可以维持 15dB 的消光比，对应于 41.6%的分数带宽。测量结果表明，所制造的结构可以在 220GHz 到 303GHz 之间实现 15dB 的消光比，对于线性和圆偏振，交叉偏振传输效率均高于 76.7%。这种半波超表面设计可以很容易地集成到紧凑的太赫兹系统中，用于各种应用。
