Experimental and theoretical study of reflection and coherent thermal emission by a SiC grating supporting a surface-phonon polariton

Polarized directional reflectivity and emissivity of a SiC one-dimensional grating are studied. Measurements and calculations are performed between 10 and 11.5 mu m where the real part of the permittivity of SiC is negative. Pronounced dips due to surface-phonon polariton excitations are observed in the reflectivity spectra inp polarization. Thermal emission displays peaks in the same directions and at the same particular frequencies. A comparison between theory and experiments shows a good agreement for both cases. The dispersion relation is obtained theoretically and experimentally. Finally, we discuss the spatial coherence of the monochromatic thermal emission. Indeed, it is shown that the existence of peaks of the emitted-monochromatic radiation, in particular angular directions, implies that, due to surface waves, the thermally excited field is partially spatially coherent along the interface.