EXPERIMENTAL AND THEORETICAL-STUDY OF REFLECTION AND COHERENT THERMALEMISSION BY A SIC GRATING SUPPORTING A SURFACE-PHONON POLARITON

Polarized directional reflectivity and emissivity of a SiC one-dimensi onal grating are studied. Measurements and calculations are performed between 10 and 11.5 mu m where the real part of the permittivity of Si C is negative. Pronounced dips due to surface-phonon polariton excitat ions are observed in the reflectivity spectra inp polarization. Therma l emission displays peaks in the same directions and at the same parti cular frequencies. A comparison between theory and experiments shows a good agreement for both cases. The dispersion relation is obtained th eoretically and experimentally. Finally, we discuss the spatial cohere nce of the monochromatic thermal emission. Indeed, it is shown that th e existence of peaks of the emitted-monochromatic radiation, in partic ular angular directions, implies that, due to surface waves, the therm ally excited field is partially spatially coherent along the interface .