Spectral analysis of Bragg gratings written in fluid-infiltrated photonic crystal fibers

The guiding properties of Bragg gratings inscribed in solid core photonic crystal fibers (PCFs) are investigated theoretically using a full vectorial Multipole Method combined with closed form expressions for the reflection response of the Bragg fiber gratings. When the PCF air-holes are infiltrated with different fluids, a downward shift is observed in the power reflectivity spectra. Both relative Bragg shift and grating´s bandwidth depend linearly on the effective refractive index which supports the potential use of such photonic crystal fiber Bragg grating (PCFBG) as optofluidic refractive index sensor as well as tunable filter. The influence of the structural parameters of the PCF on the sensitivity and bandwidth of the Bragg grating is also investigated.