Radiation Response of Distributed Feedback Bragg Gratings for Space Applications

The radiation response of distributed feedback (DFB) Bragg gratings written with continuous wave (CW) UV or IR femtosecond lasers in Ge-doped fibers was studied up to the total ionizing dose of 1 kGy(SiO
₂
) since these components are aimed to be used as the laser cavity for space applications. We demonstrated that the ultranarrow passband peaks shift of the same quantity of their Bragg peak since the cavity length cannot change at such low doses. Moreover, the studied DFBs based on type I-UV and type I-IR FBGs show a shift of 5 and 3 pm, respectively, at 1 kGy. These are very encouraging results for their use in real-space applications, but better performances could be obtained by inscribing DFBs based on type II-IR gratings in F-doped fibers since these latter show generally better radiation resistance.