Inscribing fiber Bragg gratings using IR-fs pulses and a phase-mask scanning technique: Potential and applications

Over the last decade, Fiber Bragg Gratings (FBG) have become key components for optical telecommunication systems and sensor applications due to their low losses and narrow bandwidth filtering. Using conventional writing techniques based on UV absorption requires the use of photosensitive fiber material. However, this is problematic in active fibers and, therefore, causes problems when applying this technique to fiber lasers and amplifiers. In the last years, an alternative method based on the non-linear absorption of focused femtosecond pulses allowed the inscription of FBG into non-photosensitive fibers. We report here on the inscription of such gratings using IR femtosecond pulses and a phase-mask scanning technique to produce high reflectivity gratings in various non-photosensitive fibers. The specific issues associated with the femtosecond inscription like appropriate focusing and positioning techniques necessary for high quality phase-mask scanning will be discussed. We will discuss the application in fiber lasers based on rare-earth doped fibers with integrated Bragg reflectors.