Effects of writing conditions on the photoinduced birefringence in azodye-doped polymers by a femtosecond laser

Birefringence in azodye-doped polymethylmethacrylate (PMMA) and azodye-doped inorganic–organic hybrid silica was induced by multiphoton excitation of a femtosecond laser. Comparing the growth kinetics of the photoinduced birefringence (PB) in the two matrixes, we concluded the mechanisms of photoinduced anisotropy were different and azodye-PMMA was much better for applications in optical storage. We also found that the growth rate and saturation value of the PB in azodye-PMMA were dominated by either peak or average power of the laser, strongly depended on writing conditions. An optimal control of the PB by varying writing conditions was indispensable to fully realize optical storage.