Optically Tunable Fiber Bragg Grating

This work presents the photoinduced wavelength shift of a side-polished fiber Bragg grating (SPFBG) with a photoresponsive liquid crystal (LC) overlay. The reflection peak wavelength of the SPFBG is tuned by refractive index (RI) modulation, which comes from the phase transition of the overlaid photoresponsive LC under ultraviolet (UV) light irradiation. The wavelength shift of 0.66 nm is observed with the UV light irradiation density of 0.64
$\hbox{mW/mm}^{2}$
. During the phase transition of the photoresponsive LC, the increase of RI leads to the reflected Bragg wavelength red-shift and the shift is reversible and repeatable. The photoresponsive LC-overlaid SPFBG has potential applications as an active filter in all-fiber telecommunication systems and fiber-based light sensing devices