APPLICATION OF INFRARED SEMICONDUCTORS INTERFERENCE FILTERS FOR OPTICAL SENSORS IN EXPRESS SPECTROSCOPY OF ORGANIC MATERIALS

Abstract

The presence in food and the environment of nitrates,  organic  and other substances harmful to humans can be identified by their characteristic molecular spectra in the near infrared radiation. When developing optical sensors, whose work is based on the determination of the spectral absorption  characteristics  of  organic  matter, it is necessary to apply cutting optical filters  for the selection of certain infrared ranges of the spectrum. The work carried out to develop multilayer thin film  interference  filters  with  replaceable  cutting  position  limits  infrared  radiation  depending  on  the concentration  and  type  of  the  studied  compounds. The  peculiarity  of  these  filters  is  the  use  of semiconductor  crystals  In₄Se₃,  In₄Te₃  and CdSb as  substrates  for  thin-film  multilayer  coating.  High stability  of  the  spectral  characteristics,  resistance  to  chemicals  and  atmospheric  action  of  single crystals In₄Se₃, In₄Te₃  and CdSb enables the design based on these filters with  λ =1.7-6.5 um different positions of shortwave radiation limits cutting range and a maximum transmittance T max =91-95%. The method of SEM studies depending on the structure of thin films -component filters ZnS, SiO, Ge, Te, SrF₂  on technological factors and on spectral and mechanical stability of the multilayer coating are used. The requirements to design solutions of the active cell optical biosensor developed with the use of  infrared  filters.  The method and simulation modeling to build adaptive reconfigurable computer information-measuring  system  of   rapid  analysis of qualitative composition and quantitative parameters of molecular spectra of bioactive substances are proposed.