Inscription of strong Bragg gratings in pure silica photonic crystal fibers using UV femtosecond laser pulses

We demonstrate our experimental results on inscription of strong first-order Bragg gratings in hydrogen-free and hydrogen-loaded pure silica photonic crystal fibers (PCFs) using high-intensity 160 femtosecond (fs) UV laser pulses at 266 nm and a two-beam Talbot interferometer. Bragg reflectivities up to 37 dB for the H2-loaded fiber as well as Bragg wavelength tuning over the telecom C-band using a single phase mask were achieved. The in-situ nonlinear filamentation of UV fs laser pulses, scattered by the fiber's micro-structured cladding, is demonstrated by direct refractive index profile measurement across the cross section of a written fiber. The results of thermal annealing measurements for a H2-loaded PCF are also presented.