The coupling of spontaneously emitted photons to surface plasmons in metal films is a promising technique to increase the efficiency of light-emitting devices. Here we propose and theoretically investigate the use of metallo-dielectric multiple layers to engineer the surface-plasmon density of states, so as to introduce tunable resonances in the emission efficiency through the anticrossing of modes localized on neighboring interfaces. To illustrate, large enhancements in the radiative recombination rate at tunable wavelengths are predicted for a GaN-based light-emitting device, using a structure with different combinations of the layers thicknesses.
In the limit where diverges, the frequency of each dispersion curve approaches its asymptotic value , and the penetration depth of the SP modes in the metal becomes negligibly small (see Ref. 9). As a result, in this limit SPs at different interfaces do not couple to each other regardless of the metal film thickness, and therefore their asymptotic frequencies do not vary with metal thickness.