Black gold deposits as absorbers for far infrared radiation

Abstract

Abstract Thermal infrared sensors with maximal sensitivity and minimal response time require radiation absorbing layers with small heat capacity and high absorbance. In the near infrared these conditions are well met by black gold layers. In order to examine the question whether black gold layers are suitable absorbers as well in the far infrared, their reflectance is measured in a wave number range from k = 14 to 650 cm −1 , corresponding to a range in wavelength λ = 1/ k between 15 and 710 μm. The samples are prepared at various residual gas pressures. The influence of tempering on the absorbance and the spectral absorption behavior at low temperatures is discussed. The experimental results may be accounted for by a dielectric function according to the Bergman formalism. The spectral dependence of the absorption coefficient and the real and imaginary parts of the refractive index following from it are presented.