Inverse-designed BaCO₃/TiN optical Tamm state sensors with enhanced refractive index sensitivity

Optical Tamm state (OTS) sensors are of considerable interest for biosensing applications, benefiting from strong localized field confinement and the experimental convenience of normal-incidence excitation geometry. Conventional multilayer devices based on forward design usually require exhaustive parameter scanning, making optimization inefficient in high-dimensional spaces. We present an OTS refractive-index sensor utilizing a BaCO₃/TiN/analyte/(SiO₂/TiO₂) composite structure, whose geometric parameters are globally optimized via a particle swarm optimization (PSO) algorithm. Numerical calculations show that the optimized device achieves a sensitivity of 590.4 nm/RIU and a figure of merit (FOM) of 47.3 RIU^-1. The results show that the structures improve OTS sensing performance and are promising for inverse design applications.