Plasmonic Brewster Angle: Broadband Extraordinary Transmission through Optical Gratings

Extraordinary optical transmission through metallic gratings is a well established effect based on the collective resonance of corrugated screens. Being based on plasmonic resonances, its bandwidth is inherently narrow, in particular, for thick screens and narrow apertures. We introduce here a different mechanism to achieve total transmission through an otherwise opaque screen, based on an ultrabroadband tunneling that can span from dc to the visible range at a given incidence angle. This phenomenon effectively represents the equivalent of Brewster transmission for plasmonic and opaque screens.

Figure 1

The geometry of interest and its equivalent TL model.

Figure 2

Angular transmission spectra for a grating thickness $l=200\mathrm{nm}$ and period $d=96\mathrm{nm}$. The slit width is indicated in each panel. Fourier modal method simulations (left) are compared with analytical results (right). The dashed line indicates the plasmonic Brewster angle condition.

Figure 3

Similar to Fig. 2 but for thicker screens and a larger period: $l=400\mathrm{nm}$ and $d=192\mathrm{nm}$.

Figure 4

(a) Electric field distribution $E_x$ on the $E$ plane for $l=400\mathrm{nm}$, $d=192\mathrm{nm}$, and $w=24\mathrm{nm}$ at $f=395\mathrm{THz}$ for normal incidence (left) and incidence angle ${\theta }_B=75°$ (right). (b) Power flow distribution at the Brewster angle (left) and comparison with an equivalent dielectric etalon with $\epsilon =14{\epsilon }_0$. In each panel, the fields are normalized to the same scale.