Thermal properties of fibre Bragg gratings inscribed point-by-point by infrared femtosecond laser

Direct, point-by-point inscription of fibre Bragg gratings by an infrared femosecond laser has been reported recently. Response of these gratings to annealing at temperatures in the range 500 to 1050 C is studied for the first time. Gratings inscribed by infrared fermtosecond lasers were thermally stable at temperatures up to 900degreesC, representing a significant improvement in comparison with the 'common', UV inscribed, gratings. Annealing at temperatures up to 700degreesC increased grating reflectivity.