Angle-independent plasmonic substrates for multi-mode vibrational strong coupling with molecular thin films

Vibrational strong coupling of molecules to optical cavities based on plasmonic resonances has been explored recently, because near-fields can provide in sub-diffraction limited volumes. Such field localization maximizes strength, which is crucial for modifying the vibrational response and, thereby, manipulating chemical reactions. Here, we demonstrate an angle-independent nanodisk substrate that overcomes limitations traditional Fabry-Perot cavities, design strongly couple with all surface regardless molecular orientation. We provides C=O stretch deposited films PMMA. also show large linewidths plasmon resonance allows simultaneous two, orthogonal water symmetric and asymmetric modes a thin film copper sulfate monohydrate surface. A three-coupled-oscillator model developed analyze strength these two modes. With precise control over diameter, tuned systematically through modes, both varying as function frequency, achieved simultaneously range diameters. This work may aid further studies into manipulation ground-state landscape by perturbing multiple increasing