Proton-Radiation-Tolerant Silicon Photonic Charge Sensor for Spacecraft Applications

Abstract

Silicon waveguides are promising platforms for spacecraft potential sensing owing to their compactness and immunity to electromagnetic interference. However, proton-induced optical absorption in operating silicon waveguides has not been quantitatively clarified, despite their direct exposure to the space radiation environment during spacecraft operation. Here, we present a systematic elucidation of proton-radiation effects on a photonic charge sensor based on silicon photonic crystal waveguides. During proton irradiation at 20 keV, we quantitatively evaluate the increase in optical absorption under device operation and find that a fluence of 1.0 × 10¹⁴ cm⁻² induces an additional absorption coefficient of approximately 0.41 cm⁻¹. We further demonstrate that the sensor retains its ability to measure spacecraft potential even after exposure to a high proton fluence of 1.0 × 10¹⁵ cm⁻², confirming its intrinsic radiation tolerance. These results establish the radiation robustness of silicon-waveguide-based sensing mechanisms and provide the first quantitative basis for implementing photonic charge sensors in radiation-rich spacecraft environments.