As thin metal films are known to act as wide-band absorbers for infrared radiation, in this paper Ni metal films are prepared on the Ge surface of double-sided polishing, The results showed the absorbing properties of the metal layer are strongly influenced by the dielectric function of the sensor material. This paper also describes one multi-layers structure as absorber. The structure included a reflector layer of 100-nm-thick Ti (e-beam evaporation), 2-µm-thick polyimide(spin-coating), and 14.9-nm-thick Ni film (e-beam evaporation). These contain a half transmissive thin metal film, a total reflective thin metal film and a quarter-wave polyimide film. The results showed that, measured performance matches well with theoretical predictions.