We numerically and experimentally demonstrate an ultrathin and compact Mach–Zehnder interferometer (MZI) for sensing and amplitude/phase modulations of spoof surface plasmon polariton (SSPP) waves. For a specific frequency, the magnitude and phase of the far-field transmission are modulated when a dielectric sample is loaded on one of the MZI arms. The phase difference between the SSPP waves propagating along the sensing and reference arms causes the outputs from both arms to interfere, allowing small perturbations in the sensing arm to be detected. Our study shows that the sensitivity of the proposed SSPP MZI is significantly higher than that of the single-armed SSPP waveguide, and also better than that of the conventional MZI formed with the traditional microstrip lines. The dependence of the sensitivity on the structural parameters such as geometrical parameters of the detected material and the arm length of MZI is discussed, revealing the possibility of realizing miniaturized MZI with high sensitivity.

我们通过数值和实验证明了一种超薄且紧凑的马赫-曾德干涉仪（MZI），用于对表面等离子体激元（SSPP）波进行传感和幅度/相位调制。对于特定频率，当介电样本加载到 MZI 臂之一时，远场传输的幅度和相位会被调制。沿传感臂和参考臂传播的 SSPP 波之间的相位差会导致两个臂的输出发生干扰，从而可以检测到传感臂中的小扰动。我们的研究表明，所提出的 SSPP MZI 的灵敏度明显高于单臂 SSPP 波导的灵敏度，也优于由传统微带线形成的常规 MZI。