LOW-TEMPERATURE ANOMALIES IN POLYVINYL-ALCOHOL PHOTOPOLYMERS

Acoustooptical parameters in a mixture of polyvinyl alcohol (PVA) poly mers with modified polyvinyl alcohol (MPA) were investigated as functi ons of the MPA content, time of exposure and temperature. The maximum value of the acoustooptical quality coefficient was achieved for value s of the MPA content above 70%. It was proposed to use the polyvinyl a lcohol photopolymers as acoustooptical modulators and deflectors. An e ssential influence of the polyvinyl alcohol modifications on the acous tooptical parameters was unambiguously shown. Also, a critical depende nce of the acoustooptical coefficients on the sample thickness was rev ealed. The data on the acoustooptical quality coefficient correlate we ll with the data obtained for the sound losses coefficient. (C) 1997 E lsevier Science Ltd.