Annealing of High-Temperature Stable Hydrogen Loaded Fiber Bragg Gratings

• Published in: IEEE photonics technology letters 2016-05, Vol.28 (9), p.939-942
• Main Authors: Alqarni, Sondos A., Bernier, Martin, Smelser, Christopher W.
• Format: Article
• Language: English
• Subjects: Annealing; Fiber Bragg gratings; Fiber gratings; Gratings; Indexes; Optical fiber devices; Propagation losses; Temperature sensors; Ultrafast Lasers
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2016.2518798

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 H 2 -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 high-temperature 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 high-temperature stable fiber sensors.