Characterization of Gamma Radiation Sensitivity in Cerium, Lutetium and Aluminum Doped Optical fiber with Long Period Gratings

In this work, we present the first analysis of gamma radiation response in silica optical fibers with core doped with lutetium and aluminum (LuAG). By utilizing long period gratings (LPGs) inscribed within the fibers, we monitored the evolution of their properties in real time. These fibers were fabricated using modified chemical vapor deposition technique combined with nanocrystal doping, while the LPGs were inscribed using electric arc discharge method. The LPGs were subsequently exposed to gamma radiation with total dose up to 4.5 kGy at various dose rates (0.45, 0.9, and 1.8 kGy/h). A comprehensive investigation of the dose rate dependence on their response has been conducted and post-irradiation effects have also been evaluated. A remarkable shift in the LPG resonant wavelength, up to 50 nm at the highest dose, significantly surpassing the response of standard fibers, with minimal radiation-induced attenuation, has been observed. This LPG wavelength shift is directly related to gamma radiation induced refractive index changes (RIRIC) in the fiber, a phenomenon previously unexplored in this type of fiber. This advancement paves the way for the understanding and exploitation of novel optical fiber materials in the field of ionizing radiation sensing and protection.