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A modified solid-core photonic crystal fiber (PCF)-based plasmonic sensor is proposed where light propagation through the PCF is controlled by scaling down of air holes. The modified core facilitates the easy excitation of the plasmonic surface, resulting in improved sensor performance. The chemically stable gold is externally coated on the PCF surface, which helps to establish surface plasmon resonance phenomena. The response of the sensor is analyzed based on the numerical method, and the design parameters are optimized to enhance the sensing performance. The asymmetric fiber-core structure provides the polarization controllability and significantly suppresses the y -polarized response to achieve a dominant x -polarized response and additional functionalities. The sensor exhibits a maximum wavelength sensitivity of 11,000 nm/RIU (refractive index unit) and sensing resolution of 9.09 × 10 − 6 RIU in the x -polarized mode. Also, the sensor exhibits maximum amplitude sensitivity of 631 R I U − 1 , and a good figure of merit is 157 R I U − 1 . Furthermore, the sensor can detect the unknown analytes’ refractive index (RI) in the sensing analyte RI range of 1.33 to 1.40, which will lead to finding the potential applications in biomolecules, organic chemicals, and environment monitoring.

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Light controllability, design flexibility, and non-linearity features of photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor enable high sensitivity in the field of biosensing. Here, bio-inspired butterfly-core shaped microstructure fiber-based plasmonic sensor is proposed where circular air-holes are arranged to enhance the sensing performance. Butterfly shaped core is designed to confine the incident light into the core by preventing light scattering through the cladding and helps to excite surface electron of plasmonic metal layer. Chemically stable plasmonic material gold is used to produce the SPR phenomenon. The analyte detection layer and the plasmon layer are located externally on the PCF surface to make the detection process more feasible. The sensor performance is studied based on the finite element method (FEM), and the structural parameters are tuned to obtain maximum sensor performance. This modified core-based sensor exhibits the maximum wavelength sensitivity (WS) of 56,000 nm/RIU and the amplitude sensitivity (AS) of 1,584 RIU-1 for the x-polarized mode. It also shows an improved sensor resolution (SR) of 1.8 ×10−6 RIU, along with a decent figure of merit (FOM) of 691 RIU-1. Moreover, this sensor can detect analyte refractive indexes (RI) within a broad RI range of 1.33 to 1.42 in the visible to near-infrared wavelength range (450–2100 nm). Finally, the proposed sensor may have possible application to detect organic chemicals, food quality, and diseases with high accuracy due to outstanding sensitivity and linearity.

A combination of internal and external sensing approach based plasmonic sensor is proposed to detect multiple analytes simultaneously. The sensor shows the maximum wavelength and amplitude sensitivities of 12,000 nm/RIU and 807 RIU-1, respectively for xpolarized mode.