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 × 10 14 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 × 10 15 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.