Design and analysis of a plasmonic split rings metasurface using characteristic mode theory for optical sensing

In this paper, a plasmonic metasurface is proposed and designed that has switching capability and it can be used as a quantum switch as well as an optical sensor. To provide the switching characteristic, Kerr material is used with dimer split ring resonator. The Kerr material is considered to change the response from Fano to Lorentzian shape, thus two logical values of 0 and 1 can be made at the Fano dip resonance. The Characteristic Mode Theory is investigated to predict the occurrence of the Fano response with exact wavelength. The study shows that Fano response appears when the phase of CMT modes is around 90°. As a result, the Kerr material can impact the phase of CMT modes, that makes switching characteristic for the proposed metasurface, by reducing the phase value to 40° for various Kerr material implementation in the metasurface. Also in this paper, using eigenvalues, the exact location of the Fano response, was obtained and bright and dark modes are detected without plotting characteristic currents. The proposed metasurface is developed for optical sensing with high sensitivity as a part of optical and quantum spectroscopy. The sensitivity of the sensor is obtained around 400 nm/RIU which is sufficient to distinguish the materials and to have high resolution.