Yuan Mingrui, Wang Qingwei, Li Yanfeng, Zhang Xixiang, Han Jiaguang, Zhang Weili
Appl Opt. 2020 Nov 20;59(33):10451-10456. doi: 10.1364/AO.409828.
Terahertz (THz) spoof surface plasmon polariton (SPP) waveguides can provide subwavelength confinement, which makes it possible for the THz waves to transmit at low loss over long distances along a metallic surface. This work reports on the design and actualization of an ultra-compact wavelength diplexer formed by THz spoof SPP waveguiding structures. By adding a certain number of periodic pillars in the coupling part of the directional coupler, the refractive index of the anti-symmetrically distributed odd modes can be engineered, thereby adjusting the coupling length. By adjusting the periodic pillar parameters properly, the SPP modes at two target frequencies will be coupled in the device for an odd or even number of times, so that the SPP modes at these two frequencies can be coupled out from different ports. The length of the wavelength diplexer is 1.6 mm, which is about 12.8% of its traditional counterpart. Minimum simulated transmittances of -24.34 and -26.27 can be obtained at 0.637 THz and 0.667 THz, respectively. The insertion losses at the two operating frequencies are less than 0.46 dB, and the extinction ratios are both better than 19 dB. By cascading the proposed diplexers, a compact wavelength demultiplexer with more channels can be obtained, which has important applications for future THz integrated communication systems.
太赫兹（THz）仿表面等离激元极化激元（SPP）波导能够提供亚波长限制，这使得太赫兹波有可能沿着金属表面以低损耗进行长距离传输。本文报道了一种由太赫兹仿SPP波导结构构成的超紧凑波长双工器的设计与实现。通过在定向耦合器的耦合部分添加一定数量的周期性柱体，可以设计反对称分布的奇模的折射率，从而调整耦合长度。通过适当调整周期性柱体参数，两个目标频率的SPP模将在器件中耦合奇数次或偶数次，使得这两个频率的SPP模能够从不同端口耦合输出。该波长双工器的长度为1.6毫米，约为传统双工器长度的12.8%。在0.637太赫兹和0.667太赫兹处分别可获得最低模拟透射率-24.34和-26.27。两个工作频率处的插入损耗小于0.46分贝，消光比均优于19分贝。通过级联所提出的双工器，可以获得具有更多通道的紧凑波长解复用器，这对未来太赫兹集成通信系统具有重要应用。
