Femtosecond laser processed fiber Bragg gratings in polarization-maintaining single-mode fibers for dispersion adjustment in fiber lasers

Duration: 01.04.2020-31.03.2022

Co-funded by Federal Ministry for Economic Affairs and Energy (BMWi), Germany (AiF-ZIM)

Spectral dispersion in ultrashort pulse lasers leads to unwanted broadening of the pulses. This dispersion is compensated in the case of free-space beam-propagation laser systems by using prism or grating compressors. In the case of fiber-based laser systems, either external resonator mirrors with dispersion compensating thin film structures or fiber Bragg gratings with specially adapted spectral phase profiles are used. By application of the latter so-called chirped fiber Bragg grating (cFBG), the grating distances between the grid points for example varies linearly so that the linear spectral dispersion of the light wave, propagating in the glass fiber, can be compensated.

Currently, these cFBG structural elements are commercially manufactured using the non-flexible mask process technology. Due to this, manufacturers of short-pulse fiber lasers can only fall back on a few standardized cFBG types and are strongly limited in the conception of new customer-specific fiber laser systems.