Long-range propagation of surface plasmons in a thin metallic film deposited on an anisotropic photonic crystal

We propose using a strongly anisotropic dielectric as a substrate for plasmonic devices. We show that the propagation range of surface plasmons is increased if the substrate is a birefringent dielectric crystal with a properly oriented optical axis. The increase of the propagation range depends on the degree of anisotropy, and, consequently, it turns out to be small for substrates of natural optical crystals, where anisotropy is weak. However, in specially designed photonic crystals, the anisotropy may be very strong, thus leading to appreciable increase of the propagation range. A photonic-crystal substrate, being a medium with nonlinear dispersion, also affects the dispersion law of the surface plasmon. All these effects may increase the efficiency of modern plasmonic and optoelectronic devices.