Upconverted 5d–4f luminescence from Er3+ and Nd3+ ions doped into fluoride hosts excited by ArF and KrF excimer lasers

We report on observation of upconverted VUV luminescence due to 5d–4f radiative transitions in Er3+ and Nd3+ ions doped into some fluoride crystals, under excitation by ArF and KrF excimer lasers, respectively. Only spin-forbidden 5d–4f luminescence of Er3+ (at 165 nm) was detected from the LiYF4:Er3+ crystal whereas both spin-forbidden (at 169 nm) and spin-allowed (at 160.5 nm) components are observed from the BaY2F8:Er3+ crystal, the latter being much weaker than in the case of one-photon excitation. Nd3+ 5d–4f luminescence at 180 and 173 nm has been detected from the LiYF4:Nd3+ and LaF3:Nd3+ crystals, respectively. The shift of short-wavelength edge of 5d–4f emission spectra towards longer wavelengths is observed under temperature increase from 15 to 293 K. The observed effects in the spectra of Er3+ and Nd3+ doped crystals were interpreted as a result of reabsorption of 5d–4f luminescence escaping from the bulk of the crystals.