Structure-property relationship and photoinduced birefringence of the azo and azo-azomethine dyes thin films in PMMA matrix

Here, we present previously synthesized azo and azo-azomethine dyes as thin films in PMMA matrix in order to investigate their spectral and optical properties. The spectral properties of the vapour deposited 100 nm nanosized films of the dyes have been characterized by UV-VIS and Fluorescence spectroscopy to determine the excitation and emission energies of the electron transitions. Photoinduced birefringence was induced in the films by pump lasers with wavelengths 355 nm and 491 nm in the region of the absorbance band of the chromophores used. The kinetics of recording, relaxation and erasure of birefringence were presented. The photochromic behaviour of the chromophore groups in azo dyes (-N = N-) and azo-azomethine dyes (-N = N-and CH = N-) were evaluated as potential light driven reversible optical storage devices. The presence of two photoactive groups in azo-azomethines makes them appropriate candidates for optical photoswitches.