In this article, an SPR sensor based on 12-fold quasi-periodic PCF composed of Ge-doped silica is introduced for analyte detection. The outer surface of the cladding is covered by a 40 nm gold layer serving as the plasmonic layer for the proposed sensor. The birefringence induced due to the inherent characteristic of the 12-fold pattern in the cross-section provides discrepancy for the operation of the structure regarding x- and y-polarizations. The wavelength sensitivity, amplitude sensitivity, and resolution of 12150 nm.RIU−1, 678 RIU−1, and 8.23 × 10–6 RIU, respectively are obtained for the proposed sensor. The FEM method has been implemented to investigate the performance of the proposed sensor for biosensing application in a detection range of 1.33–1.41.

A 2D hole-type hexagonal lattice photonic crystal is utilized, herein, to detect the refractive index change of the material infiltrated into the designed circular sensing area which also resembles a ring resonator. The accuracy of the detection process is enhanced considering the simultaneous shift of the resonance wavelengths and the intensity modulation which occur in two separate spectral regions. The presented structure has the ability to detect liquids, material concentrations in fluids and gases having refractive indices in the range of n = 1-2 with sensitivity and quality factor of 61 nm/RIU and 3000, respectively, for resonance-wavelength-shift-based operation. The detection range of n = 1-1.4 with the sensitivity of S = 0.69 NI/RIU is achieved for the intensity-based measurement and the results show good linearity in the operating range.

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