Radiation Sensitive Long-Period Fiber Grating Based on Tb-Doped Silica Fiber

We demonstrate a radiation sensitive long-period fiber grating (LPG) based on terbium (Tb)-doped silica fiber, fabricated by dual-sided CO2 laser exposure. At a total dose of 6.0 ± 0.2 kGy of gamma radiation, the maximum radiation-induced resonance wavelength shift (RIRWS) of LPG in Tb-doped silica fiber is up to 3.98 nm, which is much higher than that of 1.14 nm in standard single-mode fiber. To characterize the degree of modification of fibers by radiation, we calculate the radiation-induced refractive index change (RIRIC), which is as high as $1.05\times 10^{-5}$ for Tb-doped silica fiber, approximately 276.3% of that of standard single-mode fiber. In addition, the growth of RIRWS with increasing cladding mode order is analyzed, and the theoretical and experimental RIRWS of LPG are compared. This new type of LPG has great promise in the field of high-dose radiation sensing, such as dose monitoring in nuclear reactors, particle collision experiments, and so on.