Ultraviolet C-ray sensor application of heavily Cr-doped ruby

Fluorescence-enhanced photodiode (FE-PD) combining Si photodiode (Si-PD) and heavily Cr-doped rubies with Cr concentrations of 1.5–3.0 mol% was found to be sensitive to ultraviolet C-ray (UVC) light measurement. The output signal intensity from FE-PD using heavily Cr-doped rubies increases linearly in proportion to the UVC light intensity from UVC LEDs. The UVC light sensitivity of FE-PD using heavily Cr-doped rubies varies depending on the Cr concentration. The broad PL peak close to the near-infrared region at approximately λ = 774 nm observed in heavily Cr-doped rubies facilitates the UVC light sensitivity of FE-PD. This result suggests that FE-PD enhanced by heavily Cr-doped ruby is a useful UVC sensor.