Multicolour PbSe sensors for analytical applications

PbSe detectors are photoconductors with optimum response in the medium-wavelength infrared region. PbSe detectors provide fast response and high sensibility at room temperature, are rugged and show resistance to environmental conditions, providing low cost detecting devices. These properties make this detector a good candidate for a wide range of applications, including the field of gas detection. Gas detection technologies may require detection capabilities and operational performance. In order to have sensors with optimum detection of chemical compounds in vapour phase, the selectivity of PbSe has been improved by means of advanced interference filters, to allow the detection of low concentrations of chemicals species. To give the detectors an added value, PbSe detectors have been monolithically integrated with the selected interference filters. Here we report on the results obtained in order to process PbSe detectors with the spectral response modified by design. The requirements for gas detection are tight because they involve high transmittance for the pass band, broad rejection range and low transmittance value out of band. Filters designed and produced for our purpose were double Fabry-Perot cavity based interference filters. First trials with gases show good sensitivity.