Femtosecond laser written fibre bragg gratings with arbitrary reflection and dispersion profiles

We present results on the fabrication of low-loss Fibre Bragg Gratings (FBGs) that were directly inscribed into the fibre core using focused femtosecond laser pulses in a continuous core-scanning technique [1]. This method enables the fabrication of strong Type I-IR gratings with virtually arbitrary reflection and dispersion profiles. While the core-scanning technique offers the same flexibility over the grating period that is the distinctive feature of point-by-point inscribed gratings (which are typically Type II-IR damage-gratings), it also results in ultra-low scattering losses that can normally only be achieved in phase-mask written gratings. The types of structures that have been fabricated include uniform FBGs, chirped FBGs, apodised FBGs and phase-shifted gratings. All gratings were inscribed with circular polarized light in order to reduce losses associated with light scattering on nano-gratings or nano-crevices, respectively [2].