Figure 13.

Unpolarized SERS intensity of methylene blue adsorbed on gold nanowires (NWs) versus excitation polarization $\theta$ as measured in a backscattering geometry. SERS intensity was found maximum for $\theta =0°$ (inset, black line), i.e., for incident polarization vector (denoted as ${\overrightarrow{e}}_{exc}$) parallel to the nanocavity axis ${\overrightarrow{n}}_x$, and minimum for $\theta =90°$ (inset, red line), i.e., ${\overrightarrow{e}}_{exc}$ parallel to the NWs long axis ${\overrightarrow{n}}_y$. The SERS intensity profile was well fitted with the $~{\cos }^2\vartheta$ law (blue line), plus low order terms (Equation (63)). Excitation wavelength was 633 nm, thus the SERS spectrum is considered as a resonance one (SERRS). Adapted with permission from [43]. Copyright 2011 American Chemical Society.