Spectroscopic characterisation of the Tm 3+ doped KLa(WO 4 ) 2 single crystals L. Macalik a, * , J. Hanuza a,b , D. Jaque c , J. Garcı ´a Sole ´ c a Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw 2, Poland b Department of Bioorganic Chemistry, Faculty of Engineering and Economics, University of Economics, Wroclaw, Poland c Departamento de Fı ´sica de Materiales, C-IV, Facultad de Ciencias, Universidad Auto ´ noma de Madrid, 28049 Madrid, Spain Available online 21 July 2005 Abstract The spectroscopic characterisation of the Tm 3+ doped double potassium–lanthanum tungstate KLa(WO 4 ) 2 (KLWO) through the absorption, fluorescence and lifetime measurements is presented. We show absorption spectra in the visible and NIR regions recorded at room and low temperature, the luminescence spectra especially that of the 3 H 4 ! 3 H 6 transition lying in the 800 nm region which makes it suitable for diode laser pumping. The lifetimes were measured for KLa(WO 4 ) 2 with 2 at.% of Tm 3+ and the values were 112 ls, 208 ls, 1.7 ms and 5.7 ls for 1 G 4 , 3 H 4 , 3 F 4 , and 1 D 2 , respectively. The results of the Judd–Ofelt analysis are presented and discussed. The obtained intensity parameters were used to determine the radiative decay rates, radiative lifetimes and branching ratios for the Tm 3+ transitions from the excited multiplet manifolds to the lower lying manifold states. The infrared cross-section measurements were done. Ó 2005 Elsevier B.V. All rights reserved. PACS: 42.70.a; 42.70.Hj; 78.20.e; 78.55.Hx; 71.20.Eh; 71.70.d Keywords: Spectroscopic properties; Luminescence; Absorption; Tm 3+ ; KLa(WO 4 ) 2 1. Introduction Solid-state lasers have been playing an important role in the novel laser physics and quantum electronics. The fluoride host crystals and oxide crystals lead among the diversity of structure and properties of laser active crys- tals. The oxide crystals have great possibilities for stim- ulated emission excitation in different spectral ranges. The investigation of the laser crystals has become the basis for producing big-size active elements for powerful laser amplifiers with laser diode pumping and stimulates permanent searching for new laser crystalline materials and generating ions with the discovery of new SE chan- nels which could extend the spectral range to new fre- quencies [1]. The low temperature monoclinic phases of KLa (WO 4 ) 2 , KGd(WO 4 ) 2 or KY(WO 4 ) 2 are well known host materials for optically active rare earth ions like Er 3+ , Yb 3+ , Nd 3+ , Ho 3+ or Tm 3+ . These hosts can incorpo- rate high concentrations of the ions approaching the stoichiometric composition [2–4]. In addition, these laser materials are promising for diode-pumped high-power lasers, thin-disk and waveguide designs as well as for ultrashort (ps/fs) pulse laser systems [5]. There is a technological interest in Tm 3+ doped crys- tals and glasses because of their potential applications as a laser active media with emissions in the visible and mid-infrared spectral regions. Especially, the 1.8 lm region is widely examined where the Tm 3+ ions have been recognised as a dopant with interesting potential 0925-3467/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2005.05.015 * Corresponding author. Tel.: +48 71 343 50 21; fax: +48 71 344 1029. E-mail address: l.macalik@int.pan.wroc.pl (L. Macalik). www.elsevier.com/locate/optmat Optical Materials 28 (2006) 980–987