Considerations on the surface relief grating formation mechanism in case of azo-polymers, using pulse laser irradiation method

• A mechanism for SRG formation using pulse laser irradiation is proposed.
• The mechanism is based on the material deformation in the solid state.
• Azo-polyimides were investigated and compared with other azo-polymers having a more flexible main chain.
• Photoisomerization of the azo-polymers was performed in solid state and in solution.
• The ability to generate SRG from the perspective of photochromic behavior is discussed.

Azobenzene-polymers have been the subject of intensive research due to their unique and unexpected properties that allow various applications triggered by light, one of the most investigated being the capability to generate a surface relief gratings (SRG). Despite the effort to understand the SRG formation process, the mechanism remains unclear until now. The paper presents a study concerning the azo-polymer response to the pulse laser irradiation, in the context of the SRG inscription. We propose an inscription mechanism based on the material deformation in the solid state, probably induced by the azo-groups parallelization with the electric field vector. Aromatic polyimides containing azobenzene units were investigated and compared with other azo-polymers having a more flexible main chain, from the photochromic behavior’s perspective and the ability to generate SRG.