(color online) Emissivity spectra at different filling factors for (a) h = 0.1 μm and (d) h = 0.2 μm. The corresponding field intensity distributions at resonances are plotted in panels (b), (c), (e), and (f). In each field map, the vertical white dashed lines are guides for the eye and arranged with equal transverse space (same in the whole paper). For SPPs, the field intensity is distributed periodically and the white vertical lines can label its periodicity.