Highly Sensitive X-Shaped SPR Biosensor for a Wide Range of Detection

In this paper, we present a novel surface plasmon resonance (SPR) based X-shaped photonic crystal fiber (PCF) biosensor designed to achieve high sensitivity and a wide range of detection capabilities. The design and simulation were performed using the finite element method (FEM) with a perfectly matched layer boundary-based mode solver. Our results show that the suggested sensor can accurately detect analyte refractive indices (RI) in the range of 1.25 to 1.42. The sensor achieves a maximum wavelength sensitivity(WaS) of 29,000 nmJRIU and a resolution of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.72\times 10^{-6}\text{RIU}$</tex>, along with a maximum amplitude sensitivity(AmS) of 1581 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{RIU}^{-1}$</tex> and a highest figure of merit (FOM) of 558. These impressive sensitivities are the result of a carefully optimized design strategy, which involved selecting optimal geometric and material parameters. The sensor's high performance suggests its potential for use in detecting various biological samples, making it a valuable tool for medical diagnostics and environmental monitoring. However, practical implementation may face challenges such as fabrication precision and material compatibility, which are discussed in detail.