Fabrications of Fiber Bragg Gratings Written inPhotonic Crystal Fibers

We report a two-beam interference method employing a femtosecond or excimer laser to write fiber Bragg gratings in the pure-silica and Ge-doped photonic crystal fibers (PCFs). The effects of the H2-loading and Ge-doping techniques on the efficiency of grating inscription were investigated by measuring the development of Bragg wavelength and attenuation in the transmission spectra with increasing exposure dose. H2-loading dramatically enhances the laser-induced index modulation not only in Ge-doped PCFs but also in pure-silica PCFs