Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 μm, as well as high emissivity up to 0.65 at a wavelength of 3.7 μm. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization.
US 9,400,219 B2
Iowa State University Research Foundation, Inc.
Lee, Jae-Hwang; Ho, Kai-Ming; and Constant, Kristen P., "Metallic layer-by-layer photonic crystals for linearly-polarized thermal emission and thermophotovoltaic device including same" (2016). Iowa State University Patents. 327.