Fig. 8

P-polarized extinction as a function of wavelength and angle of incidence, of Au two-dimensional structure with a period of 500 nm unannealed (a) and annealed at 400 °C for 15 min (b) overlapped with the dispersion curves calculated from Eqs. (1) and (2): the dispersion curves of the surface plasmon polaritons corresponding to the air-metal interface (1, 1′, 2′) and substrate-metal interface (1s, 1s′, 2s, 2s′) for m = +1 (1, 1s), m = +2 (2s), m = −1 (1′, 1 s′) and m = −2 (2s′) diffraction orders. The color bar shows extinction with red representing high extinction