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

Area of Science:

• Plasmonics
• Molecular Spectroscopy
• Chemical Physics

Background:

• Plasmonic near-fields enable strong light-matter coupling in sub-diffraction volumes.
• This coupling is essential for modifying molecular vibrations and chemical reactions.
• Traditional optical cavities face limitations in coupling strength and molecular orientation dependence.

Purpose of the Study:

• To demonstrate an angle-independent plasmonic nanodisk substrate for enhanced molecular coupling.
• To overcome limitations of Fabry-Pérot cavities.
• To achieve simultaneous strong coupling to multiple vibrational modes.

Main Methods:

• Fabrication of angle-independent plasmonic nanodisk substrates.
• Characterization of coupling with PMMA (polymethyl methacrylate) C=O vibrational stretch.
• Investigation of simultaneous coupling to orthogonal water vibrational modes in copper sulfate monohydrate.
• Application of a three-coupled-oscillator model to analyze coupling strength.

Main Results:

• Demonstrated strong coupling with PMMA C=O vibrational stretch.
• Achieved simultaneous strong coupling to two orthogonal water vibrational modes.
• Showcased tuning of plasmon resonance and Rabi splitting via nanodisk diameter control.
• Confirmed simultaneous strong coupling to multiple modes over a range of diameters.

Conclusions:

• The developed plasmonic nanodisk substrate enables angle-independent, strong vibrational coupling.
• This platform allows for simultaneous perturbation of multiple molecular vibrational modes.
• The findings facilitate future studies on manipulating molecular chemical landscapes and enhancing coupling in nanoscale volumes.