Graphene Plasmon Enhanced Vibrational Sensing of Surface-Adsorbed
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Abstract
We characterize the influence of graphene nanoribbon plasmon excitation
on the vibrational spectra of surface-absorbed polymers. As the detuning
between the graphene plasmon frequency and a vibrational frequency
of the polymer decreases, the vibrational peak intensity first increases
and is then transformed into a region of narrow optical transparency
as the frequencies overlap. Examples of this are provided by the carbonyl
vibration in thin films of poly(methyl methacrylate) and polyvinylpyrrolidone.
The signal depth of the plasmon-induced transparency is found to be
5 times larger than that of light attenuated by the carbonyl vibration
alone. The plasmon-vibrational mode coupling and the resulting fields
are analyzed using both a phenomenological model of electromagnetically
coupled oscillators and finite-difference time-domain simulations.
It is shown that this coupling and the resulting absorption enhancement
can be understood in terms of near-field electromagnetic interactions