Refractive index biosensor based on topological ring resonator

The hemoglobin (Hb) concentration in the blood is an important parameter in the field of medical diagnostics. It is no doubt that improving robustness and reducing unnecessary losses needs to be reviewed with special attention in the detection Hb process. Topological ring resonator (TRR) structure based on all-dielectric valley photonic crystals (VPCs) has started to gain the interest of researchers due to its anti-scattering properties and unique immune defect performance. In this paper, we demonstrated Hb concentration detection using the TRR structure based on all-dielectric VPCs. It can be seen that a high transmittance even if there are structural defects of the flat-, Z-, and Omega -shape waveguide when the structure is immersed in water completely. Going further, by using a triangular ring-shaped topological edge coupled to the straight topological edge waveguide, which excites a narrowband high-quality (Q) factor resonance. The strong dependence of the resonant peak on Hb concentration and the consequent refractive index (RI) is the essential bases of the detection process. Results show that the sensitivity of the structure can reach up to 798.39 nm/RIU with a figure of merit (FOM) as high as 725.81 RIU-1 (65 g/L). Due to the high sensitivity and topologically protected nature, the proposed structure has great potential in Hb detection, which is hardly affected by structure imperfections and disorder.