Polarization Dependence of Surface Enhanced Raman Scattering in Linear Nanoantennas with Spectrally Distinct Plasmon Resonances

Antonino Foti Istituto Processi Chimico-Fisici, IPCF-CNR, Messina, Italy Cristiano D'Andrea Istituto Processi Chimico-Fisici, IPCF-CNR, Messina, Italy Andrea Toma Nanostructures Department, Istituto Italiano di Tecnologia, Genova, Italy Barbara Fazio Istituto Processi Chimico-Fisici, IPCF-CNR, Messina, Italy Elena Messina Istituto Processi Chimico-Fisici, IPCF-CNR, Messina, Italy Onofrio M. Maragò Istituto Processi Chimico-Fisici, IPCF-CNR, Messina, Italy Enzo Di Fabrizio PSE and BESE Divisions, King Abdullah University of Science and Technology, Jeddah, Saudi Arabia Marc Lamy de La Chapelle Laboratoire CSPBAT, CNRS (UMR 7244), Université Paris 13, Bobigny, France Pietro Giuseppe Gucciardi Istituto Processi Chimico-Fisici, IPCF-CNR, Messina, Italy

Here we show that, through the selective excitation of the short- or the long- axis LSPR, it is possible to control and totally rotate (90°) the polarization of the Surface Enhanced Raman Scattering (SERS) of randomly oriented molecules adsorbed on linear nanoantennas. By a proper design of the nanoantenna, this can be accomplished switching the excitation wavelength from the visible to the NIR, while using orthogonal fields polarizations, so to match the two distinct LSPRs. Modeling the nanoantenna enhancement with wavelength-dependent field enhancement tensors we recover the relations ruling the parallel-polarized and unpolarized- SERS intensity dependence found experimentally when selectively driving the two LSPRs. Our results support a physical picture in which the strongly coupled molecule-nanoantenna system behaves as an hybrid structure whose energy levels are determined by the molecule while the far-field radiation properties are determined by the antenna modes.

foti@ipcf.cnr.it