Visualization of surface plasmon polariton waves in two-dimensional plasmonic crystal by cathodoluminescence.

A cathodoluminescence technique using a 200-keV transmission electron microscope revealed the dispersion patterns of surface plasmon polaritons (SPPs) in a two-dimensional plasmonic crystal with cylindrical hole arrays. The dispersion curves of the SPP modes involving the Γ point were derived from the angle-resolved spectrum patterns. The contrast along the dispersion curves changed with the polarization direction of the emitted light due to the property of the SPP modes. The SPP modes at the Γ point were identified from the photon maps, which mimicked standing SPP waves in a real space. The beam-scan spectral images across the plasmonic crystal edge clearly demonstrated the dependence of the SPP to light conversion efficiency on the emission angle and polarization of light.