Abstract

Fibre Bragg gratings (FBGs) are key components in fibre laser development, and femtosecond laser inscription has paved the way for highly stable and robust monolithic fibre laser systems [1]. There are two fundamental approaches for femtosecond laser inscription of FBGs: phase mask scanning [2] and the point-by-point (PbP) [3] technique. The phase mask technique offers high period stability and reproducibility but limited flexibility over the grating period. The PbP technique offers complete flexibility in the grating period; in fact local phase shifts and continuous chirp have been demonstrated [4]. However these gratings exhibit significant scattering loss [5]. Zhou et al. [6] proposed a new writing technique where 4^th order gratings where inscribed line by line; however these still show high scattering losses. We present a core-scanning technique for FBGs using a PbP inscription setup that benefits from the flexibility over the grating period, but has drastically reduced scattering losses.

© 2013 IEEE