Optically Induced Surface Relief Gratings in Polymer Films Doped With Sulphonyl Group Containing Azobenzene

Abstract

In holography, more attractive have become azobenzene compounds doped in a polymer matrix (host-guest polymer film) or chemically attached to the polymer. Azobenzene molecules exhibit reversible photoisomerization between trans- and cisisomers which can form a surface relief grating in the films. The authors investigate the holographic recording and formation of surface relief gratings in a host-guest polymer film with two original azobenzene compounds. Holographic recording with 325 nm laser light was performed in host-guest polymer films with the host being polymethylmetacrylate (PMMA) and the guest – 15 wt% azobenzene molecules (A-45 or A-48). In both cases an increase in the diffraction efficiency at the beginning of the process could be related to the trans-cis-photoisomerization, while the second increase − to the formation of surface relief gratings. The systems with A-45 molecules reach a diffraction efficiency of 0.7%, and with A-48 molecules − of 0.24%. Also, the depth of surface relief gratings is greater in the films with A-45 (35 to 45 nm) than in those with A-48 (4 to 6 nm) molecules.