Plasmonic and Photonic Refractive Index Biosensor Based On Bound States In The Continuum

Abstract In this paper, we propose a novel structure for biosensors based on a diffraction grating to diagnose four types of cancers cells. This biosensor is used to detect Hela, Jurkat, PC12, MDA-MB-231 and MCF-7 cancerous cells, based on their refractive indices. The present configuration consists of a glass layer covered by a gold layer, a grating coated by a silicon nitride layer separating the sensor from sensing medium. Bound states in the continuum (BIC) in a hybrid plasmonic-photonic structure can be achieved at Γ point and off-Γ. The symmetry-protected BIC is formed at the Γ-point of the periodic system due to the strong coupling between plasmonic or photonic modes. On the other hand, the Friedrich-Wintgen (FW) BICs can be readily achieved off-Γ due to the strong coupling between plasmonic and photonic modes. A comparative study is made on the basis of three BICs (plasmonic BIC, photonic BIC, and FW-BIC). Here, numerical analysis based on the Rigorous coupled-wave analysis method (RCWA) is performed to optimize the biosensor sensitivity, by also considering the full width at half maximum (FWHM), detection accuracy (DA), and figure of merit (FoM). The FW BIC-based biosensor for photonic mode exhibits the highest S of 1208nm/RIU, low FWHM of 0.5 nm, the maximum DA of 2 nm −1 , and best FoM of 2416 RIU −1 .