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Femtosecond inscription of semi-aperiodic multi-notch fiber Bragg gratings using a phase mask

: Goebel, T.A.; Heusinger, M.; Krämer, R.G.; Matzdorf, C.; Imogore, T.O.; Richter, D.; Zeitner, U.D.; Nolte, S.

Volltext ()

Optics Express 28 (2020), Nr.24, S.35682-35694
ISSN: 1094-4087
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IOF ()
Fiber Bragg Gratings; infrared devices; ultrafast lasers; ultrashort pulses; upper atmosphere

We 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.