Physical effects in the VIS-IR of ionizing gamma radiations on indium fluoride optical fibers

The use of fiber optic technologies in space exploration offers significant advantages due to their low weight, high sensitivity, and immunity to electromagnetic interference. However, their performance under ionizing radiation remains a critical challenge. This study investigates the effects of gamma irradiation on multimode indium fluoride optical fibers (IFG-InF3), with the aim of evaluating their suitability for infrared spectrometers in harsh environments, such as planetary exploration missions. The fibers were exposed to 1.25 MeV gamma rays at the ENEA Casaccia Calliope facility at three total doses: 125, 250, and 375 Gy. Comprehensive analysis of transmission spectra in both the VIS-NIR and MIR ranges was conducted before and after irradiation, over a time span of eight months. The results demonstrate a significant degradation of transmittance in the visible range, particularly below 0.5 μm, with a partial recovery observed over time. Minimal impact was noted in the MIR range. These findings support the viability of IFG-InF3 fibers for applications above 1 μm in radiation-exposed environments and contribute to the advancement of radiation-resistant fiber-optic technologies for space instrumentation. This work is part of the ASI-INAF TRIS (Transmission and Illumination System) research and development program, which has the goal of increasing the TRL (Technology Readiness Level) of current transmission and illumination systems operating in the visible and near-infrared ranges by using new fiber optics technologies.