Continuously chirped fiber Bragg gratings by femtosecond laser structuring

We report on what we believe to be the first successful inscription of continuously chirped fiber Bragg gratings (CCFBG) into a nonphotosensitive single-mode fiber (SMF) with near-IR femtosecond laser pulses. The continuous chirp was achieved by inscribing into a bent fiber using a phase mask scanning technique. We fabricated a 20 mm long CCFBG with a bandwidth of 6 nm and a maximal reflectivity of 50%. The second-order dispersion of the CCFBG of up to 28 ps(2) was measured with spectral interferometry.