Localized excitation of polarized light emission by cathodoluminescence spectroscopy.

Surface plasmons (SPs), the resonance of free electrons on the metal-air interface, may strongly interact with light and generate some extraordinary optical effects. Instead of using conventional planar light excitation, here we excite SPs with a focused electron beam on metallic nanostructures with different geometrical symmetries. With the help of a polarizer and filter in the detection system, we obtain cathodoluminescence (CL) images with different polarizations at certain wavelengths. The maxima in the CL images show that the focused electron beam may efficiently excite luminescence with different polarizations at different spots. Comparing the data collected on the structures with specific geometrical symmetry, we demonstrate that the polarization of the emitted light depends on both the structural symmetry and the excitation location. We suggest that this Letter is enlightening to understand the relationship between the SP resonance on the structure and the emission of CL with different polarizations.