Comparison of the radiation hardness of silicon Mach-Zehnder modulators for different DC bias voltages

Radiation hard optical links are the backbone of read-out systems in high-energy physics experiments at CERN. The optical components have to withstand large doses of radiation and provide high data rates. Silicon photonics is currently being considered a promising technology to replace electrical and optical links in future experiments. It has already been demonstrated that integrated silicon Mach-Zehnder modulators can withstand a high neutron fluence and large total ionizing doses. Before read-out systems based on these components can be taken into consideration, it has to be determined how biasing affects their radiation hardness. For this reason we prepared bonded and fiber-pigtailed prototypes and irradiated them with x-rays. We found that under reverse-bias the radiation hardness of the tested components is reduced in comparison to un-biased samples. However, we were able to show that one device type can withstand the radiation without phase shift degradation up to 1 MGy despite the accelerated degradation due to biasing.