Space-variant polarization manipulation of a thermal emission by a polar material subwavelength grating supporting surface phonon-polaritons

Space-variant polarization manipulation of enhanced omnidirectional thermal emission in a narrow spectral peak is presented. The emission is attributed to surface phonon-polariton excitation from space-variant subwavelength SiO2 gratings. Polarization manipulation was obtained by discretely controlling the local orientation of the grating. We experimentally demonstrated thermal emission in an axially symmetric polarization distribution. We show that by coupling surface phonon-polaritons to a propagating field, large anisotropy of the emissivity is obtained within a narrow spectral range. We experimentally demonstrate this effect by fabricating a space-variant subwavelength grating on a SiO2 substrate to encrypt an image in the polarization state of a thermal radiation field. Theoretical calculations based on rigorous coupled-wave analysis are presented along with experimental results.