Phonon-mediated magnetic polaritons in the infrared region.

Magnetic polaritons that couple electromagnetic waves with magnetic excitation can be used for tailoring the radiative properties of materials in energy-harvesting and other applications. Previous studies used metallic microstructures to induce magnetic responses. With rigorous coupled-wave analysis (RCWA), transmission enhancement with a SiC slit array and coherent thermal emission with a SiC deep grating is theoretically demonstrated in the infrared within the phonon absorption band. The field distributions and the agreement in the resonance frequencies predicted from both RCWA and LC circuit models strongly suggest that magnetic polaritons exist in the SiC microstructures. This type of magnetic polariton is mediated by vibration of atoms in polar materials (i.e., optical phonons), rather than by free electrons in metals. Our results suggest that phonon-mediated magnetic polaritons have promising applications such as filters and selective coherent emitters in the infrared spectral region.