Voigtlander, C.C.VoigtlanderKrämer, R.G.R.G.KrämerGoebel, T.A.T.A.GoebelRichter, D.D.RichterNolte, S.S.Nolte2022-03-052022-03-052016https://publica.fraunhofer.de/handle/publica/24324110.1364/OL.41.000017We report on the inscription of fiber Bragg gratings using femtosecond laser pulses and the phase-mask technique. The wavefront of the inscription laser is variably tuned with a spatial light modulator (SLM). By applying Fresnel lenses with different focal lengths, the period of the fiber Bragg gratings could be shifted. A linear change of the grating period for a FBG inscribed with a third-order deformed wavefront and a quadratic-period behavior for a fourth-order wavefront could be verified experimentally for the first time.en535journal article