We have developed an analytical model that provides a mechanistic description of the plasmonic enhancement of vibrational signals by infrared nanoantennas. Our treatment is based on a coupled-point-dipole model which considers the interaction between a point-like nanoantenna and a single vibrational dipole moment. This idealized model is refined in two consecutive steps. The first step generalizes the model to make the treatment of non-point-like nanoantennas possible. The second step deals with local-field effects originating from the mutual interaction of the molecular vibrations. We have compared the results of our model with finite-difference time-domain simulations, and we find that our model predicts both the lineshapes and the amplitudes of the vibrational signals in a quantitative manner. Our analysis shows that the local-field effects play a surprisingly dominant role in the plasmonic enhancement, and we discuss possibilities of engineering this local field in order to further boost the plasmonic amplification.

Additional Metadata
Publisher OSA
Persistent URL dx.doi.org/10.1364/OE.24.012202
Journal Opt. Express
Citation
Rezus, Y.L.A, & Selig, O. (2016). Impact of local-field effects on the plasmonic enhancement of vibrational signals by infrared nanoantennas. Opt. Express, 24(11), 2202–2227. doi:10.1364/OE.24.012202