Arc-shaped gold-coated photonic crystal fiber for enhanced surface plasmon resonance biosensing
摘要
This study presents the design and FEM-based analysis of two photonic crystal fiber (PCF) surface plasmon resonance (SPR) biosensors featuring a 90° arc-shaped gold coating. Two geometries-a point-top hexagonal structure and a flat-top structure with a 60° rotated second ring-were examined to evaluate the influence of air-hole arrangement on plasmonic response. Analysis of x- and y-polarized modes revealed resonance wavelengths of ~ 0.645 μm and 0.67 μm for the point-top design, and ~ 0.675 μm and 0.67 μm for the flat-top design at an analyte refractive index of 1.37. The flat-top configuration exhibited stronger effects on birefringence and field confinement. Confinement-loss peaks reached 0.74 and 37.5 dB/cm (point-top) and 11.68 and 37.13 dB/cm (flat-top) for x- and y-polarizations, respectively. Increasing the analyte index from 1.36 to 1.40 resulted in higher confinement loss and a redshift in resonance wavelength. Maximum wavelength sensitivities were 10,000–10,333 nm/RIU (point-top) and 11,667–13,000 nm/RIU (flat-top). Polynomial fits revealed a strong linear relationship between resonance wavelength and analyte refractive index. The adjusted R² values were 0.9836 and 0.9489 for the x-polarized designs, and 0.9209 and 0.9306 for the y-polarized designs. Estimated resolutions ranged from 1 × 10−5 to 9.67 × 10−6 RIU (x-polarized) and 7.69 × 10−6 to 8.57 × 10−6 RIU (y-polarized), demonstrating high detection precision. Overall, the results underscore the critical role of air-hole geometry and polarization in optimizing SPR-PCF biosensor performance.