High infrared light yield of Erbium-doped fluoride crystals

The emission spectrum of Erbium-doped fluoride crystals excited by soft X-rays in the (400-1700) nm wavelength range is investigated between 3.2 K and 300 K. The largest component of the crystals emission is observed in the infrared range, which corresponds to a light yield of several tens of photons/keV. Such a large value is caused by energy transfer processes between the Erbium ions which convert the excitation of a dopant ion at high energies into the emission of multiple infrared photons. The present results show that this mechanism could be exploited to realize scintillators of high light yield.