Phase-shifted Bragg grating inscription in photonic crystal fibers by UV phase mask beam stop technique

There are several techniques available for fabrication of phase-shifted gratings in single mode fibers. Yet, very few studies have examined inscription of such gratings in photonic crystal fibers (PCFs). In this paper, we report what we believe to be the first demonstration of the phase-shifted grating inscription in PCFs using a phase mask and a beam stop. The grating inscription is demonstrated for three hexagonal lattice PCFs with different air-filling fractions. The transmission spectra of the fabricated gratings reveal phase shift resonance peaks with a -3 dB bandwidth between 40 and 80 pm which is up to 4 times narrower than of the resonances of uniform Bragg gratings inscribed in the same fibers.