Two-photon excitation to 4f65d configuration of Gd3+ in LiGdF4 crystal by KrF excimer laser

The two-photon excitation to high-lying levels of Gd3+ via the intermediate DJ6 levels in LiGdF4 and GdF3 crystals has been studied under pumping by 248 nm radiation from a KrF excimer laser. Luminescence in the UV (204 nm), orange (570-640 nm) and IR (720-810 nm) regions, which is due to GJ6-S7/28, GJ6-PJ6 and GJ6-IJ6 transitions in Gd3+, respectively, has been observed from the LiGdF4 crystal at room temperature. No radiative transitions from the 4f7GJ6 levels of Gd3+ have been detected from the GdF3 crystal. It was assumed that at low temperatures the two- photon excitation of the LiGdF4 crystal with a KrF laser could result in the observation of short-wavelength upconverted VUV luminescence at ∼127 nm due to 4f65d-4f7S7/28 transitions in Gd3+ .