Holographic grating stability: influence of 4,4'-azobis (4-cyanopentanoic acid) on various spatial frequencies

This paper presents the results obtained when holographic gratings were stored with a spatial frequency of 954 and 2663 lines/mm in transmission geometry and 4600 lines/mm in reflection geometry in a polyvinyl alcohol/acrylamide-based material. Photopolymers are materials that give good results at low frequencies, but their diffraction efficiency (DE) decreases at high frequencies. A chain transfer agent, 4,4'-azobis (4-cyanopentanoic acid) (ACPA) was incorporated in the material composition to improve spatial resolution. Furthermore, a curing process was applied to the stored gratings in order to maintain the DE stable over time. The DE and shrinkage for symmetric holographic transmission and reflection gratings were measured to evaluate their quality and quantify the improvement produced by ACPA.