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.

OSA
dx.doi.org/10.1364/OE.24.012202
Opt. Express

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