We compare the isothermal and isochronal annealing response of ultrafast laser-induced first-order gratings to that of the third-order gratings up to 1000 °C. Both devices are written in H2 -loaded SMF-28 fiber with low-energy femtosecond laser pulses. With the first-order gratings, we observed a regeneration process that allows for a final peak index change of roughly 4% of the original grating. A higherature stable peak reflectivity of 39% is obtained (-2.14-dB transmission loss). The third-order gratings do not anneal out completely (they do not regenerate) and roughly 26% of the device persists at 1000 °C corresponding to a final peak reflectivity of 24% (-1.17-dB transmission loss). Due to their similar fabrication conditions, these findings suggest a strong link between the regenerated first-order gratings and the stable third-order devices. We estimate that both first- and third-order gratings of ~4.5 mm in length are good candidates for the development of higherature stable fiber sensors.

Additional Metadata
Keywords Fiber Bragg gratings, Temperature sensors, Ultrafast Lasers
Persistent URL dx.doi.org/10.1109/LPT.2016.2518798
Journal IEEE Photonics Technology Letters
Alqarni, S.A. (Sondos A.), Bernier, M. (Martin), & Smelser, C. (2016). Annealing of higherature stable hydrogen loaded fiber bragg gratings. IEEE Photonics Technology Letters, 28(9), 939–942. doi:10.1109/LPT.2016.2518798