A plasmonic refractive index sensor based on a metal-insulator-metal waveguide coupled with a double concentric square ring resonator is proposed and analyzed both theoretically and numerically. The theoretical and the numerical results are based on the transmission-line model and the finite difference time domain method, respectively. The theoretical results agree well with the numerical ones. A maximum sensitivity of 1250 nm per refractive index unit with a high figure of merit of 32.8 for the double concentric square ring resonator with one stub is obtained in the near-infrared region. Also, the double concentric square ring resonator with three stubs is simulated, and has a maximum sensitivity of 1270 nm per refractive index unit with a high figure of merit of 58. Our proposed plasmonic structures could find useful applications in sensing systems and integrated circuits in the near-infrared region.

提出了一种基于金属-绝缘体-金属波导耦合双同心方环谐振器的等离子体折射率传感器，并在理论和数值上进行了分析。理论和数值结果分别基于传输线模型和时域有限差分法。理论结果与数值结果吻合良好。对于具有一个短截线的双同心方环谐振器，每个折射率单位的最大灵敏度为1250 nm，品质因数为32.8，在近红外区域中获得最高灵敏度。此外，还模拟了具有三个短线的双同心方环谐振器，每个折射率单位的最大灵敏度为1270 nm，品质因数为58。