High- Q band edge mode of plasmonic crystals studied by cathodoluminescence

We have investigated the quality factor (Q-factor) of the band edge modes in the plasmonic crystal by a cathodoluminescence technique. We have found that the Q-factor at the Γ point depends on the terrace width (D)/period (P) ratio of the plasmonic crystal. The finite-difference time-domain methods predict that the band edge mode at D/P = 3/4 has a high-Q-factor (Q ∼ 250 by Palik's permittivity data and Q ∼ 530 by Johnson and Christy's data). The beam-scan spectral images allowed us to visualize the standing surface plasmon polariton waves at the band edge energies, and a high-Q-factor of ∼200 was observed at D/P ∼ 3/4.