Impact of Ionizing Radiation and Thermal Annealing on the Electrooptic Response of Silicon Photonics Ring Modulators

Micro-ring modulators (RMs) are state-of-the-art devices for converting electrical signals into optically modulated signals, fabricated using silicon photonics (SiPhs) integrated platforms. We report the results of two X-ray irradiation tests on such devices, reaching a total ionizing dose (TID) of 12.3 MGy(SiO2), relevant for high-energy physics (HEPs) applications. For the first time, the electrooptic frequency response of RMs was measured online during irradiation, alongside the static modulation efficiency (ME). The devices exhibited degradation in both static and dynamic performance with ionizing radiation, showing strong temperature dependence. Nevertheless, the use of built-in μ -heaters enables thermal annealing that restores more than 90% of the preirradiation functionality. We also demonstrated that thermal annealing during irradiation enabled nearly complete performance recovery, after which subsequent radiation damage followed almost the same trend observed at the onset of exposure. Finally, eye diagram measurements confirm complete recovery of RM performance after annealing, with results comparable to nonirradiated devices. These findings support the feasibility of using SiPhs-based modulators for operation in harsh radiation environments such as deep space and HEP experiments.