Infrared laser radiation induced changes in the IR absorption spectra of thin polymer films

The presented work demonstrates that powerful laser radiation causes change s in absorbance spectra of epoxy resin and polyethylene. Thin polymer films were located between IR AgBrCl optical fibres and exposed to the radiation of a CO? laser. The output of the laser source was varied in the range 0-8 .5 W. Absorbance spectra were measured by a Fourier transform IR spectropho tometer. It was revealed that characteristic absorbance peaks of polymers d ecay under the powerful IR light. The apparent dependence of peak magnitude on IR radiation power has been established. The mathematical theory of the observed effect was worked out. The authors suggest that the effect under discussion is caused by the oxygen-free thermal action of IR radiation on t he chemical structure of polymer materials. The revealed effect could be ef fectively used for the lowering of losses in adhesive contacts of IR optic elements. The novelty of the proposed method lies in the fact that thermal treatment is localized strictly in the adhesive contact: optical elements t o be contacted (fibres, lenses etc), which are highly transparent in the IR , do nor experience the LR radiation, but the polymer adhesive is subjected to a temperature rise. The phenomenon could be effectively used for the lo wering of losses in optical contacts and recording and storage of informati on in polymer films as well.