High-quality retroreflecting fiber Bragg gratings were written in standard Ge-doped telecom fiber (Corning SMF-28) after a few minutes exposure with pulsed 800-nm, 120-fs laser radiation by use of a deep-etch silica zero-order nulled phase mask optimized for 800 nm. Induced index modulations of 1.9×10<sup>-3</sup> were achieved with peak power intensities of 1.2×10<sup>13</sup> W/cm<sup>2</sup> without any fiber sensitization. The fiber gratings are stable and did not erase after 2 weeks at 300 °C. The primary mechanism of induced index change results from a structural modification to the fiber core.
© 2003 Optical Society of America
(230.1480) Optical devices : Bragg reflectors
(320.2250) Ultrafast optics : Femtosecond phenomena
(320.7140) Ultrafast optics : Ultrafast processes in fibers
(350.3390) Other areas of optics : Laser materials processing
Stephen J. Mihailov, Christopher W. Smelser, Ping Lu, Robert B. Walker, Dan Grobnic, Huimin Ding, George Henderson, and James Unruh, "Fiber Bragg gratings made with a phase mask and 800-nm femtosecond radiation," Opt. Lett. 28, 995-997 (2003)