A localized SPR D-shaped fiber optic sensor utilizing silver grating coated with graphene: Field analysis

Abstract

A D-Shaped fiber optic plasmonic sensor with silver grating coated with graphene is proposed in this paper. The proposed structure is compared to planar silver, grating silver, and planar silver with graphene grating. Performance defining parameters based on transmittance curves [resonance wavelength (λr), shift in λr (δλr), minimum transmittance (Tmin), and bandwidth (BW)] as well as based on field intensity [penetration depth (PD) and propagation length (PL)] are determined and compared. The proposed structure has the highest λr, δλr, and lowest Tmin, indicating that it has a high sensitivity. However, its BW is slightly larger than that of other structures, which deteriorates its detection accuracy. Furthermore, the proposed structure's PD and PL are the lowest of all the other structures. At different refractive indices of sample, the PD of the proposed structure (33 nm–55 nm) is one significant digit lower than others (232 nm–299 nm). As a result, the proposed structure acts as a localized surface plasmon resonance (LSPR) sensor, which may be utilized to detect molecules with a dimension of less than 50 nm, such as viruses and cancer cells provided that these molecules should adhere on the graphene surface.