Numerical Analysis of High Sensitivity Refractive Index Sensor Based on Quad-Core PCF-SPR

Despite the advancements in SPR-based sensing technology, current designs struggle with balancing high resolution and sensitivity, the capability for multiplexed detection, and wide operational wavelength ranges. To address these limitations, this work presented a comprehensive numerical investigation of a quad-core PCF-SPR sensor featuring elliptical air holes designed for highly sensitive refractive index measurements. The sensor structure features elliptical and circular air holes. The elliptical is coated with different thicknesses of gold layers to optimize sensing performance. Besides, another gold layer with different thicknesses is coated over the whole sensor. The design enables the support of both x- and y-polarization modes, leading to enhanced capabilities of detection. The sensor attained maximum wavelength shifts of 8000 nm/RIU and 5000 nm/RIU for the x-polarization and y-polarization, respectively, which demonstrated a highly responsive sensor. Furthermore, amplitude sensitivity values reached 1300 RIU-1 for x-polarization and 1000 RIU-1 for y-polarization at a refractive index of 1.44. By optimizing the gold layer thickness, the sensor resolution was calculated to be 7.23 x 10-6 RIU, further indicating its high precision in refractive index detection. The operational wavelength range spans the visible to infrared regions, providing versatility for various sensing applications. The proposed quad-core PCF shows the ability to sense shifts across a broad wavelength range (visible to near-infrared), making it suitable for applications in biosensing, environmental monitoring, and chemical analysis.