Black Phosphorus-Assisted Plasmonic Enhancement in D-Shaped Photonic Crystal Fibers for Advanced Biomedical Sensing

This study presents the design and performance evaluation of a novel plasmonic biosensor
based on a D-shaped photonic crystal fiber (D-PCF) integrated with a black phosphorus
(BP)–gold multilayer structure, termed BP-DPCF-Sense. Aimed at enhancing biosensing
sensitivity, spectral sharpness, and stability, the sensor leverages the anisotropic plasmonic
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Black Phosphorus-Assisted Plasmonic
Enhancement in D-Shaped Photonic Crystal
Fibers for Advanced Biomedical Sensing
RESEARCH Published: 27August 2025
Volume 21, pages 929–944 (2026) Cite this article
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Plasmonics
properties of BP to strengthen the interaction between the guided core mode and surface
plasmon resonance (SPR) at the metal–dielectric interface. Finite element method (FEM)
simulations reveal that the optimal configuration—comprising a 5 nm BP layer beneath a
gold film and encapsulated by a 10 nm Al₂O₃ coating—achieves a high refractive index
sensitivity of 1800 nm/RIU and a figure of merit (FOM) of 200, outperforming conventional
gold-only and graphene-enhanced designs. The Al₂O₃ capping layer addresses BP’s known
environmental instability, preserving resonance characteristics over extended periods under
simulated oxidation conditions. Additionally, the study introduces a multiplexed design
wherein varying BP thicknesses across spatially discrete zones produce distinct resonance
peaks, allowing simultaneous detection of multiple analytes such as glucose, neuron�specific enolase (NSE), and heavy metal ions. Experimental validation confirms close
agreement with simulated data, showing less than 3.1% deviation in sensitivity
measurements. This innovative hybrid architecture not only elevates the performance
metrics of fiber-based plasmonic sensors but also offers a robust, scalable, and application�ready platform for real-time, label-free biosensing in clinical diagnostics, environmental
monitoring, and biochemical analysis. The proposed sensor framework represents a
significant advancement in nanophotonic biosensor technology by addressing the
longstanding trade-offs between sensitivity, stability, and multiplexing capability. The
sensor’s novelty lies in its hybrid plasmonic multilayer architecture, environmental stability
via dielectric encapsulation, and multiplexed detection within a single fiber segment