Fiber Bragg gratings (FBG) made with a phase mask and 800 nm femtosecond radiation

FBG's were written in SMF-28 fiber, without fiber sensitization, using 800 nm 120 fs pulses and a phase mask (peak intensities: 1.2/spl times/10/sup 13/ W/cm/sup 2/). Gratings with /spl Delta/n=1.85/spl times/10/sup -3/ and low polarization dependence were stable at 500/spl deg/C.