Journal of Luminescence 102–103 (2003) 318–326 Spectroscopic properties of new Yb 3+ -doped K 5 Bi(MoO 4 ) 4 crystals H. Ca * nibano a , G. Boulon a, *, L. Palatella a , Y. Guyot a , A. Brenier a , M. Voda b , R. Balda b , J. Fernandez b a Physical Chemistry of Luminescent Materials, Claude Bernard/Lyon 1 University, LPCML-UMR CNRS 5620 B # at. A. Kastler, 10 rue Amp " ere, La Doue 69622 Villeurbanne Cedex, France b Applied Physics Department I, E.T.S.I.I. y Telcom., Alda. Urquijo s/n, 48013 Bilbao, Spain Abstract This research work analyzes the spectroscopic properties of Yb 3+ ion in a new oxide single crystal belonging to the potassium bismuth molybdate family with the following concentrations: K 5 Bi 1x Yb x (MoO 4 ) 4 (x ¼0.005, 0.05, 0.15). We are dealing with temperature and concentration dependences of both s and p polarizations of the IR absorption and emission spectra. Raman spectra is used to interpret electronic Stark levels and vibronic levels. Concentration dependence of fluorescence lifetimes allows the measurement of the high radiative lifetime in the range 1.89–1.93ms and shows a strong self-trapping process which has been seen up to 15% Yb 3+ . Competition with a non-radiative energy transfer by up-conversion process is also observed due to the presence of Er 3+ ion as unexpected impurity. Yb 3+ pairing and clustering has not been observed in the molybdate host in which the two distances between Bi 3+ next nearest crystallographic sites seem rather too large to give any observable anti-Stokes signal by cooperative luminescence. r 2003 Elsevier Science B.V. All rights reserved. PACS: 78.55.m; 78.20.e Keywords: Laser crystals; Yb 3+ -doped oxides; Energy levels 1. Introduction Yb 3+ is indeed the most promising ion that can be used in a non-Nd 3+ laser in the near-IR spectral around 1030nm for all solid-state laser sources under InGaAs laser diode pumping between 900 and 980nm. The Yb 3+ ion has several advantages compared with Nd 3+ ion due to its very simple energy level scheme, constituting of only two 2 F 7/2 and 2 F 5/2 levels. There is no excited state absorption, no cross-relaxation pro- cess and no more up-conversion internal mechan- ism able to reduce the effective laser cross-section and, in addition, the intense and broad Yb 3+ absorption lines are well suited for IR laser diode pumping. We have recently investigated spectro- scopic properties of several Yb 3+ -doped single crystal oxides and a new general method of *Corresponding author. Tel.: +33-4-72-43-26-61; fax: +33- 4-72-44-82-71. E-mail address: boulon@pcml.univ-lyon1.fr (G. Boulon). 0022-2313/03/$-see front matter r 2003 Elsevier Science B.V. All rights reserved. PII:S0022-2313(02)00526-4