Comparison of growth dynamics and temporal stability of Bragg gratings written in polymer fibers of different types

摘要

We compare the dynamics of the Bragg gratings formation in a microstructured polymer fiber made of pure PMMA and step-index PMMA fiber with a core made of PMMA/PS copolymer. The gratings were fabricated using a standard phase mask method. In the fiber with a PMMA/PS core, based on the rate of the Bragg peaks' height and bandwidth rise versus the irradiation time, we identified three phases of the grating growth, named respectively type I, mixed and type II gratings. In the pure PMMA microstructured fiber we did not observe a significant increase in the Bragg peaks' width during the inscription. We have monitored the behavior of the gratings for 8 months since the fabrication and demonstrated significant differences in the long-term stability depending on the grating type.