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 femtosecond laser has been reported recently. Response of these gratings to annealing at temperatures in the range 500 to 1050/spl deg/C is studied for the first time. Gratings inscribed by infrared femtosecond lasers were thermally stable at temperatures up to 900/spl deg/C, representing a significant improvement in comparison with the ´common´, UV-inscribed, gratings. Annealing at temperatures up to 700/spl deg/C increased grating reflectivity.