Goebel, T.A.T.A.GoebelHeusinger, M.M.HeusingerKrämer, R.G.R.G.KrämerMatzdorf, C.C.MatzdorfImogore, T.O.T.O.ImogoreRichter, D.D.RichterZeitner, U.D.U.D.ZeitnerNolte, S.S.Nolte2022-03-062022-03-062020https://publica.fraunhofer.de/handle/publica/26562510.1364/OE.405498We present an innovative concept of a semi-aperiodic phase mask design that enables the realization of multi-notch fiber Bragg gratings (FBG). This design utilizes the overlap and interference of near-infrared ultrashort laser pulses diffracted by short sequenced phase mask sections, which not only allows for a highly stable and reproducible inscription of a large number of wavelength filters but also paves the way towards full aperiodic phase masks. The semi-aperiodic FBG inscribed by this phase mask enables versatile notch filters showing multiple non-equidistant resonances. Those filters target applications, for instance in ground-based telescopes, where a large number of hydroxyl emission lines emitted in the upper atmosphere at near-infrared wavelengths restrict the observation of faint extraterrestrial objects.enFiber Bragg Gratingsinfrared devicesultrafast lasersultrashort pulsesupper atmosphere620621journal article