Fiber Bragg grating inscription based on optical filamentation of UV femtosecond laser pulses

We present the fabrication and characterization of strong first-order Bragg gratings operating around 1550 nm in standard telecom fibers (SMF-28) by use of 160 fs UV laser pulses at 266 nm and a Talbot interferometer. Bragg reflectivities exceeding 50 dB are achieved in both hydrogen-free and hydrogen-loaded fibers. In addition, Bragg wavelength tuning over the telecom C-band using a single phase mask is demonstrated. We also show that the formation of Bragg gratings, relying on a two-photon absorption process, is intimately accompanied by the optical filamentation process of UV fs laser pulses during nonlinear propagation in the fiber.