SiO2–Silver Metasurface Architectures for Ultrasensitive and Tunable Plasmonic Biosensing

Here, we indicate that metasurface-based biosensors consisting of silver-metasurface with SiO2 and working in the near-infrared (NIR) spectral range can obtain simultaneous high-sensitivity and high-tunable detection of biomaterials including ether with n = 1.3, ethylene glycol with n = 1.4, chlorobenzene with n = 1.5, and quinolone with n = 1.6, where n is refractive index. Using 3D-FDTD method, we numerically extract the optical characteristics of the metasurface sensor and validate by quasi analytic coupled mode theory (CMT). By changing the refractive index of the dielectric layer, maximum sensitivity equal to 658 nm/RIU for Δn = 0.25 is achieved, so it can be able to use in high sensitive plasmonic sensors. Also the results show that the proposed metasurface sensor can be used as a multi-usage structure, such as biomaterial distinguish and identify TE and TM polarization at 40° incident angle (anisotropy in TE mode absorption spectra). Moreover by using silver as the metal layer, maximum and minimum group indexes are achieved as 350 and 486, respectively, so it is a good choice to utilize in harnessing of slow/fast light propagation. The overall size of the sensor is 540 nm × 540 nm × 560 nm, hence is a proper candidate for nanoscale sensor.