High energy irradiation effects on silicon photonic passive devices

In this work, the radiation responses of silicon photonic passive devices built in silicon-on-insulator (SOI) technology are investigated through high energy neutron and ⁶⁰Co γ-ray irradiation. The wavelengths of both micro-ring resonators (MRRs) and Mach-Zehnder interferometers (MZIs) exhibit blue shifts after high-energy neutron irradiation to a fluence of 1×10¹² n/cm²; the blue shift is smaller in MZI devices than in MRRs due to different waveguide widths. Devices with SiO₂ upper cladding layer show strong tolerance to irradiation. Neutron irradiation leads to slight changes in the crystal symmetry in the Si cores of the optical devices and accelerated oxidization for devices without SiO₂ cladding. A 2-µm top cladding of SiO₂ layer significantly improves the radiation tolerance of these passive photonic devices.