Self-Similar Elliptical Plasmonic Metasurface for Midinfrared Sensing

Abstract

Optical metasurfaces have emerged as promising platforms for tailoring light-matter interactions at the nanoscale. In this article, a novel self-similar metasurface is developed, comprising two rows of elliptical gold elements on a silicon dioxide (SiO ${}_{2}$ ) substrate serving as the optical layer. These elements are arranged radially on concentric rings, enabling a dual-band response. Two distinct resonances are observed at wavelengths of 4.9 and $9.8~\mu $ m, respectively. The specific arrangement of the metasurface structure provides a Fano response at the second resonance. At the first resonance, the metasurface exhibits a Q-factor of approximately 47, while the Q-factor increases to around 885 at the second resonance. The metasurface structure is further explored for sensing applications, demonstrating high sensitivity at the first and second resonances, with sensitivity values of 1088 and 340 (nm/RIU), respectively. In addition, figures of merit (FOM) are calculated to quantify the overall performance of the metasurface. The FOM values obtained for the first and second resonances are 10.88 and 30.90 (RIU⁻¹), respectively. This study showcases the potential of the proposed optical metasurface design for efficient dual-band and sensing applications.