Observation of strong yellow emission for high-conductivity ZnO excited by sub-terahertz gyrotron beam

We observed yellow light emission from ZnO single crystals with high conductivity by the irradiation of sub-terahertz waves from gyrotrons. The emitted spectrum has a broad peak around 2 eV. As the spatial distribution of yellow light reflects the gyrotron beam profile and is visible with bare eyes, the high-conductive ZnO single crystals may be applied as an imager of gyrotron beam patterns usable for quick beam diagnosis.