Multilayer coating-assisted gold-encapsulated tilted fiber Bragg grating biosensor design

To cope with up high rise in healthcare demands and accurate clinical decisions the fiber Bragg grating (FBG) sensors have performed superior over the traditional analog sensors for varied clinical decisions. The higher sensitivity and resolution toward accurate sensing make FBG a viable technology for clinical decision systems including biomechanical sensing, physiological sensing, non-invasive surgery, and biosensing. Depth assessment indicates that the encapsulated tilted FBG (TFBG), and surface plasmon resonance sensors have performed satisfactorily; yet, their suitability over the different operating conditions such as temperature, viscosity-change, noise, etc., remains suspicious. The at-hand biosensors fail to demodulate the response accurately once the surrounding refractive index approaches the cladding index. It requires a sufficiently large spectrum shift to demodulate and predict biosensing yield. To achieve it, in this paper, a multilayer coating-assisted gold-encapsulated TFBG biosensor is proposed. The proposed TFBG biosensor was designed with the grating angle of \(10^{ \circ }\) ${10}^{\circ }$ , while gold encapsulation was done to improve resolution and sensitivity. To improve biosensing toward protein analysis and immunological assessment at first gold plating was done to improve reflectivity, while graphene oxide (GO) coating was done to enhance plasmonic attraction for biosensing. In function, GO coating served dual purposes including improved antibody and antigen absorption that helped sensitivity as well as yields sufficiently large spectra change to make detection decisions. More specifically, GO coating enables the trapping of the target molecules that eventually increases the refractive index of the coating material and hence undergoes a shift in the wavelength spectra, which is used for biosensing tasks. The higher refractive index of the coating material over the cladding index results in spectral shift and coupling wavelength shifts which helps target biosensing tasks. Simulations confirmed wavelength spectrum shift signifying biosensing tasks including protein analysis and immunological assessments for clinical decisions.