基于人工表面等离激元的太赫兹低损耗传输线及带阻滤波器设计

Design of Terahertz Low-Loss Transmission Line and Band-Stop Filter Based on Spoof Surface Plasmon Polaritons

提出了一种基于人工表面等离激元(SSPPs)的太赫兹低损耗传输线,并通过加载开口谐振环(SRR)实现了具有大抑制深度的太赫兹带阻滤波器。采用不规则阶梯渐变过渡结构对SSPPs传输线进行了优化,降低了其在太赫兹频段下的传输损耗及不平坦度。通过色散分析揭示了加载SRR和不加载SRR的SSPPs传输线的频段抑制机理。加载SRR的SSPPs传输线工作在基模和一阶高次模两种模式下,其基模具有低通特性,一阶高次模具有带通特性,实现了具有通带-阻带-通带-阻带的太赫兹滤波特性。通过调节SRR的几何参数,可控制SSPPs滤波器的阻带频率;通过增加SRR的加载数量,可增大SSPPs滤波器的抑制深度。为了验证设计的可行性,采用微纳加工技术分别制作了所提出的SSPPs传输线和滤波器,并进行了太赫兹在片测试。测试结果表明:在0.11~0.17 THz频带范围内,SSPPs传输线的插入损耗小于0.5 dB/mm,回波损耗优于10 dB;SSPPs滤波器在0.142~0.156 THz频率范围内的抑制深度大于10 dB,最大抑制深度为45 dB@0.148 THz;实验结果与仿真结果具有良好的吻合度。该研究对太赫兹等离激元集成系统研究具有重要意义。

In this paper,a terahertz low-loss transmission line based on spoof surface plasmon polaritons(SSPPs)is proposed,and a terahertz rejection filter with high isolation is demonstrated by loading split-ring resonators(SRRs).The SSPPs-based transmission line is optimized by an irregular gradient transition structure,and thus its transmission loss and unevenness in the terahertz frequency band are reduced.Then,the frequency band suppression mechanisms of the SSPPsbased transmission line loaded with SRRs and without SSRs are revealed through the dispersion analysis.When the SSPPs-based transmission line loaded with SRRs operates under the fundamental mode and the first-order high mode separately,its fundamental mode is characterized by low pass while its first-order high mode features bandpass,and thus the terahertz filtering characteristic of pass-stop-pass-stop is achieved.In addition,by adjusting the geometric parameters of SRRs,we can control the stop-band frequency of the SSPPs-based filter and improve the suppression depth of the SSPPs filter by increasing the number of loaded SRRs.To demonstrate the feasibility of the design,this study conducts terahertz on-wafer tests for the proposed SSPPs-based transmission line and filter prepared by micro-nano fabrication.The results reveal that in the frequency band of 0.11-0.17 THz,the insertion loss of the SSPPs-based transmission line is less than 0.5 dB/mm,and the return loss is better than 10 dB;in the frequency band of 0.142-0.156 THz,the suppression depth of the SSPPs-based filter is greater than 10 dB,and the maximum suppression depth is up to 45 dB at 0.148 THz.The experimental results are in good agreement with the simulated ones.The research is of great significance to the integrated system of terahertz plasmons.