Tunable dual-phase TMOKE sensor in a Weyl semimetal–plasmonic waveguide

• Introduced innovative TMOKE dual-phase sensors based on surface plasmon waveguide resonance in Weyl semimetal structures. • These sensors were designed for the simultaneous detection of analytes in gaseous and aqueous environments. • The designed sensor achieved high sensitivity and a high FOM for both media, facilitating highly precise detection capabilities. • The structure generates near-perfect TMOKE signals and versatile sensing across both media without reconfiguration or geometry optimization. • Active resonance tuning via Weyl semimetal Fermi energy modulation enables dynamic, post-fabrication control of the sensor's range. We propose a dual-phase optical sensor utilizing the transverse magneto-optical Kerr effect (TMOKE) in a Weyl semimetal (WSM)-plasmonic waveguide structure. The design enables high-performance refractive index sensing in both gaseous and aqueous environments without structural reconfiguration. Numerical simulations yield sensitivities of 500 nm/ R I U (gas) and 1000 nm/ R I U (aqueous), with figures of merit (FOM) of 714 R I U - 1 and 1429 R I U - 1 , respectively. This performance is among the highest reported for dual-phase sensors. A key innovation of this sensor lies in its active tunability via the Fermi energy of the WSM, exploiting its topological properties to adapt to varying refractive indices dynamically. This work introduces a versatile platform for contactless optical sensing, with applications in biomedical diagnostics.