Effect of Radiation on a Mach–Zehnder Interferometer Silicon Modulator for HL-LHC Data Transmission Applications

High-speed Mach-Zehnder interferometer silicon modulators were irradiated with neutrons and X-rays in two separate radiation tests. The devices were exposed to a total fluence of 1.2 ×10
¹⁵
neutrons/cm
²
and a total ionizing dose of 1.3 MGy; levels comparable to the worst radiation levels for a tracking detector after 10 years of operation at the High-Luminosity LHC. Our measurements indicate that the devices' performance does not significantly degrade after exposure to nonionizing radiation and begins to be affected by ionizing radiation after a dose of a few hundred kGy; the phase-shift for an applied reverse bias of 1 V is 10% of its preirradiated value after 600 kGy of received ionizing dose.