Broadband and high transmission of Mie-resonance-coupled subwavelength metal aperture

Abstract

Transmission of the subwavelength metal aperture excited by the surface plasmon resonance is much higher than that from the Bethe theory. However, due to the sensitivity of resonant frequency and the loss of metal in optical band, it is difficult to achieve broadband and high transmission of the subwavelength metal aperture through surface plasmon resonance. In this article, the broadband and high transmission of the subwavelength metal aperture is realized when Mie-resonant-coupled silicon nanoparticles placed on both sides of the metal aperture are used to replace the surface plasmon resonance. The full wave simulation results show that bandwidth of the transmission coefficient more than 90% of the subwavelength aperture (<inline-formula><tex-math id="M1">\begin{document}$ {r \mathord{\left/ {\vphantom {r {\lambda = 0.1}}} \right. } {\lambda = 0.1}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201121_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201121_M1.png"/></alternatives></inline-formula>) reaches 65 nm by using Mie-resonance-coupled silicon nanoparticles. Compared with the transmission induced by surface plasmon resonance, the peak value is improved by 1.5 times and the 3 dB bandwidth is widened by 17 times. According to the coupled mode theory, the equivalent circuit model of transmission of the subwavelength metal aperture added with Mie-resonance-coupled silicon nanoparticles is established, and the element parameters in the circuit model are inversed under the critical coupling state. Further research shows that transmission rule of the subwavelength metal aperture added with Mie-resonance coupled silicon nanoparticles can be accurately revealed by changing the coupling coefficient in the equivalent circuit model, and the results are consistent with the full wave electromagnetic simulation results. The mathematical expression of the interaction between light and Mie-resonance-coupled subwavelength metal aperture is found, therefore it can inspire us to construct certain functional modules in optical field according to circuit design method.