Theoretical investigation of polarization-dependent surface plasmon resonance in D-shape fibers

A new approach of determining surface plasmon resonance (SPR) wavelength based on the polarization dependence has been suggested. A D-shape fiber with gold coating on the top surface has been demonstrated for the verification of this new approach. From the simulation experiment it is found that the resonance wavelength coincides with the zero-birefringence point of two orthogonally polarized degenerate fundamental modes, thus the new approach can locate the resonance wavelength of the system more accurately compared to the conventional approach, which analyzes the peak of the loss spectrum. The new approach also reveals better performance in terms of computational efficiency by computing only the real part of the refractive index. Applications of the new approach in high sensitivity measurement are discussed. A 10^-6 ambient refractive index unit measurement sensitivity and a 10^-4 fiber core ellipticity detection limit for pressure sensing have been demonstrated.