Engineering of the extraordinary optical transmission of metallic gratings via Er³⁺-doped tellurite glass

Although the properties of extraordinary optical transmission (EOT) due surface plasmon polariton (SPP), which are coupled in metallic slits have been widely studied in the last two decades, their influence on the absorption and transmission spectra from their dielectric substrates has not been deserved the same attention. The choice of a good substrate for implementation not just for gratings, but also for other devices, it is extremely important in order to achieve great applications of the EOT. Good candidates to replace the conventional semiconductor based substrates are the rare earth ions (REI) doped glasses. The specific case of Erbium ions and its implementation into glasses for the fabrication of fiber optics, as Erbium doped fiber amplifiers (EDFA). The transmission observed through the plasmonic nanostructures is elucidated considering the following effects: (i) white light absorption by the Er3+ ions, (ii) coupling between the light and the nanostructure via the creation of surface plasmon polariton where the wavelengths with minimums transmission corresponds to the ⁴I_15/2 → [²H_9/2, ⁴F_3/2, ⁴F_5/2, ⁴F_7/2, ²H1_1/2, ⁴S_3/2, ⁴F_9/2] absorption levels the Er³⁺, which propagates through the slits, and, finally, (iii) the Er³⁺ transmission intensity and the spectral shape -symmetry depend on the nature of metallic film and the number of slits constituting the arrays, for which the resonant properties are strongly affected. Furthermore, in order to compare the influence of substrate in the transmission properties, we also performed the same measurements on slit arrays fabricated on the BK 7 glass.