Plasmonic Biosensor Based on Ag-TiO2-ZnO Gratings for Cancer Detection in the Optical Communication Band

In this study, we present a novel surface plasmon resonance (SPR) sensor based on Ag-TiO2-ZnO gratings, operating in the optical communication band (1260–1625 nm), for early cancer detection. Numerical analysis using the finite element method (FEM) was employed to obtain simulation results. The proposed SPR biosensor is capable of detecting various cancer cells with refractive indices ranging from 1.368 to 1.401 in the human body. With HeLa cells used as a reference, we analyzed the effects of incident angle, Ag and TiO2 thicknesses, and grating variables on the figure of merit (FOM) of the sensor. Additionally, sensitivity, full-width half maximum (FWHM), detection accuracy (DA), and resonance depth were considered as performance parameters to evaluate the proposed optical biosensor. According to the numerical simulation results, the sensitivity of the sensor to cervical (HeLa), blood (Jurkat), adrenal (PC12), and breast (MDA-MB-231 and MCF-7) cancer cells was found to be 8537.23, 9138.72, 10558.57, 11881.43, and 12633.57 nm/RIU, respectively. The maximum FOM reached 91.7471 RIU
$^{-{1}}$
. Furthermore, we showed the distribution of the electric field along the normal direction of the resonant surface under the resonant condition of the proposed structure. It was found that the proposed structure exhibits a strong electric field enhancement effect under the resonant condition, and the penetration depth (PD) of the decayed electric field intensity was measured to be 410 nm. The numerical results obtained in this study demonstrate higher FOM and sensitivity compared to previous studies. Based on these results, we believe that the designed SPR sensor has great potential for early cancer diagnosis in the field of medical science.