Metasurface-enhanced photothermal imaging and biomolecule detection

We present a plasmonics metasurface-integrated photothermal heterodyne imaging (M-PHI) system, which leverages the strong near-field enhancement of engineered metasurfaces to amplify photothermal signals. While photothermal heterodyne imaging is a widely used label-free technique for visualizing chemical bonds, its sensitivity is constrained by the inherently low absorption cross-section of molecules in the mid-infrared. By integrating a plasmonic metasurface, the M-PHI system enhances absorption at the vibrational signatures of molecules, achieving over a 12-fold enhancement in imaging signals. This advancement enables the detection of biomolecules at concentrations below 400nM without surface functionalization.