The spectral radiative properties of coherent thermal emission in the mid- and far-IR from two metal-semiconductor resonating structures were demonstrated experimentally. Using an efficient implementation of Rigorous Coupled-Wave Analysis, a truncated resonator was designed to selectively emit at mid-IR and far-IR wavelengths. A High Impulse Power Magnetron Sputtering deposition technique was used to fabricate two Ag-Ge-Ag resonating structures with layer thicknesses of 6-240-160 nm for one sample and 6-700-200 nm for the other. Reflectance measurements demonstrated spectrally selective absorption at the designed mid- and far-IR wavelengths whose general behavior was largely unaffected by a wide range of incident angles. Further, radiance measurements were taken at various high temperatures, up to 601 K, where spectrally selective emission was achieved through wave interference effects due to thermally excited surface waves. From these radiance measurements, spectral emittance was directly derived and compared to the emittance inferred from reflectance measurements. It was established that inferring emittance through Kirchhoff’s law can help to approximate the expected emission from a structure, but it is not an exact method of determining the actual emittance of a thermal source at higher temperatures due to the temperature dependence of material parameters.

Date Published: 9 October 2012
PDF: 15 pages
Proc. SPIE 8457, Plasmonics: Metallic Nanostructures and Their Optical Properties X, 845736 (9 October 2012); doi: 10.1117/12.930397

Published in SPIE Proceedings Vol. 8457:
Plasmonics: Metallic Nanostructures and Their Optical Properties X
Mark I. Stockman, Editor(s)