A bifunctional SPR biosensor based on α -MoO₃ operating in visible to near-infrared range

Abstract Recent years have witnessed widespread adoption of α -phase molybdenum trioxide ( α -MoO₃) in biosensing owing to its in-plane anisotropic characteristics. We propose a bifunctional surface plasmon resonance biosensor employing the Kretschmann configuration that operates in the visible to near-infrared wavelength range and demonstrates a bifunctional capability defined by two core features: (1) In the wavelength-interrogation mode, the in-plane anisotropy of α -MoO₃ allows active performance tuning— x -polarization achieves high sensitivity ( S x = 8250 nm RIU −1 ), while y -polarization achieves a high figure of merit ( FOM y = 570.89/RIU). (2) The same sensor configuration also supports robust resonance angle-shift detection, confirming its versatility as a multi-mode platform.