Investigation of the influence of temperature and annealing on the radiation hardness of silicon Mach-Zehnder modulators

Optical links are vital components in the data transmission systems of High Energy Physics (HEP) experiments at CERN. With the ever-higher beam fluxes achieved by the Large Hadron Collider (LHC) the optical components have to withstand higher radiation levels and handle ever-increasing data volumes. To face these challenges, the use of Silicon Photonics (SiPh) Mach-Zehnder modulators (MZMs) in the next generation of optical transceivers for HEP experiments is currently being investigated. In this work the dependence of the radiation hardness of custom-designed SiPh MZMs on temperature is reported, including the observed improvement in radiation tolerance at low operating temperatures that are closer to the typical temperatures found in HEP experiments. Furthermore, post-irradiation annealing measurements of the devices were performed. An effective annealing method has been found by applying a forward current to the MZMs, leading to an almost immediate and full recovery of the device after irradiation up to 3 MGy. This enhanced device recovery method could effectively increase the radiation hardness tremendously in applications with low dose rates and periodic shut-down times.