Optimized magneto-optic multilayer structures for enhanced surface plasmon resonance detection

We present theoretical and numerical investigations of multilayer magneto-optic (MO) structures optimized for enhanced surface plasmon resonance (SPR) sensing using the transverse MO Kerr effect. Three configurations incorporating noble metals (Au, Ag), ferromagnetic cobalt (Co), and titanium (Ti) adhesion layers were analyzed using the transfer matrix method and finite-difference time-domain simulations at a wavelength of λ=785 nm. The effects of material selection and layer sequencing on near-field enhancement and angular sensitivity were evaluated. Among the tested structures, a configuration consisting of Au (4 nm)/Co (2 nm)/Ag (35 nm)/Ti (2 nm) exhibited the best performance, with detection limits of D=5.67×10−7 RIU for SPR and 4.8×10−8 RIU for MO-SPR modes. Here, D is defined as the minimum detectable refractive index change based on a system angular resolution of σ=5.0×10−4. These results demonstrate a promising strategy for designing compact, high-sensitivity MO-SPR sensors for biomedical, environmental, and biosensing applications.