Radiation filters and emitters for the NIR based on periodically structured metal surfaces

The spectrally selective optical properties of wavelength selective radiati on emitters and filters based on periodically microstructured metal surface s were investigated. Metal surfaces were structured by the use of a hologra phic mask and subsequent etching processes. Due to the microstructure, ther mally excited surface plasmons couple to electromagnetic radiation. Therefo re a structured tungsten surface can act as a selective radiation emitter. The calculation of the absorptance by a rigorous diffraction theory allows the prediction of the emissivity of such structures. The angle dependent em issivity of tungsten gratings with periods of 1.4 mu m and 2.0 mu m was mea sured. A peak emissivity of 70% at a wavelength of 1.6 mu m was achieved. B and pass filters for the near infrared spectral range based on perforated m etal films were investigated theoretically and experimentally. Filters with a grating period of 2.0 mu m were produced. A peak transmittance of 80% at a wavelength 2.9 mu m was achieved. The optical properties of the diffract ive elements described partly show a strong angle dependence.