Fano Resonance Sensor Based on Microhole Array Waveguides for Ultrasensitive Label-Free Biosensing.

Enhancing the sensitivity of surface plasmon resonance (SPR) sensors is of paramount importance for the detection of trace biomolecules. In this study, we innovatively developed a Fano resonance biosensing platform based on photon-plasmon coupling enhancement. The sensor consists of a poly(methyl methacrylate) (PMMA) microhole array waveguide, an MY-131-MC (MY) dielectric layer, and a silver-based plasmonic layer. This structural design enables the precise modulation of the spatial coupling between the localized photonic field and the microhole membrane, allowing the electromagnetic field of the probe light to effectively overlap with the microhole array waveguide. Furthermore, the three-dimensional interconnected microstructure enhances the light-matter interaction strength. Experimental results demonstrate that the sensor achieves an ultrahigh sensitivity of 56.24 μm/RIU in refractive index (RI) detection, representing an 11.4-fold improvement over traditional Fano-type sensors (4.9 μm/RIU). The figure of merit (FOM) is elevated to 2998.94 RIU, surpassing conventional SPR sensors by 2 orders of magnitude. The platform was employed to detect the tumor biomarker carcinoembryonic antigen (CEA), achieving a measurement sensitivity of 4.03 nm/(ng/mL) and a limit of detection (LOD) of 81.8 pg/mL. Additionally, the proposed method exhibits excellent selectivity, repeatability, and stability. This simple and cost-effective approach provides a novel strategy for developing high-performance SPR sensors for biosensing applications.