VUV spectroscopy of KYF4 crystals doped with Nd3+, Er3+ and Tm3+

Emission, excitation and absorption spectra as well as luminescence decay kinetics of KYF4 crystals doped with Nd3+, Er3+ and Tm3+ were studied in the VUV spectral range. It is shown that all the crystals have intense VUV luminescence due to interconfiguration transitions originating from the 5d states of the rare earth (RE) ions and terminating on the 4f states. The UV luminescence caused by intraconfiguration 4f-4f transitions in the RE ions is also observed from the crystals doped with the Nd3+ or the Er3+ ions under 4f-5d excitation. The spin-allowed 5d-4f luminescence from the crystals doped with Er3+ or Tm-3+ is extremely weak, i.e. there exists very efficient nonradiative relaxation from higher lying 5d states to the lowest 5d level responsible for spin-forbidden luminescence. This peculiarity of the studied crystals doped with Er3+ Or Tm3+ is very attractive for developing VUV solid-state lasers based on the crystals of such a type. (C) 2000 Elsevier Science B.V. All rights reserved.