Energy level structure and excited-state absorption properties of Er^3+-doped KPb_2Cl_5

Rare-Earth-Doped Low Phonon Energy Halide Crystals for Mid-Infrared Laser Sources

“…As a matter of fact, for this non degenerate level one expects one single line per substitution site, provided that the second crystal field sublevel of the ground state 3 H 4 does not contribute to the absorption signal shape : as it lies at 15 cm -1 , it should not be significantly populated at temperatures lower than 21.6 K. Figure 12 clearly shows the presence of five absorption lines and consequently as many substitution sites for Pr 3+ ions in KPb 2 Cl 5 , giving a beginning of explanation to the origin of the inhomogeneous band broadening, which consequently dominates the homogeneous broadening at low temperature [Ferrier et al, 2008b]. This characteristic is consistent with the structural description of the point defects ], but if it is so, why does Er 3+ or Eu 3+ substitution lead to majoritarily one type of point defect [Cascales et al, 2005;Ferrier et al, 2007;Gruber et al, 2006;Velázquez et al, 2009] In Figure 13, we see that these energy transfers do not only occur undistinctly in KPb 2 Cl 5 and in CsCdBr 3 , but that they also occur in the former compound with Pr 3+ ions concentrations a hundred times weaker. The Pr 3+ ion pairing in CsCdBr 3 , favourable to energy transfers described above, can be related to the decrease by a factor of 4 of the relative intensity of the emission issued from ( 3 F 2 , 3 H 6 ) levels in favour of those issued from ( 3 F 4 , 3 F 3 ) levels.…”

“…However, as a great number of non equivalent defects is likely to form (for instance, more than one hundred in KPb 2 Cl 5 ) and the point group symmetry is very low for all the atomic positions, the precise characterization of the Er 3+ incorporation sites in both compounds remains difficult. Crystal-field calculations with C s /C 2 point groups lead to a satisfactory agreement between experimental and calculated energy levels [Ferrier et al, 2007[Ferrier et al, , 2008aGruber et al, 2006].…”

“…This investigation demonstrated that the effect of ETU (see in Fig. 6) turns out to be completely negligible until the concentration of 3.3 mol % is achieved in KPb 2 Cl 5 crystals [Ferrier et al, 2007] (which corresponds to an average Er 3+ -Er 3+ distance of ~12 Å), and that optical pumping at 800 nm, that is, at the absorption peak in KPb 2 Cl 5 :Er 3+ , does not lead to substantial excited state absorption losses towards the 2 H 9/2 level (see in Fig. 5).…”

“…Table 1. Laser-related crystallographic, thermal, mechanical, optical and spectroscopical properties of selected low phonon energy halide crystals [Aleksandrov et al, 2005;Atuchin et al, 2011;Cockroft et al, 1992;Doualan & Moncorgé, 2003;Ferrier et al, 2006aFerrier et al, , 2007Ferrier et al, , 2008aFerrier et al, , 2008bFerrier et al, , 2009aFerrier et al, , 2009bHeber et al, 2001;Isaenko et al, 2008Isaenko et al, , 2009aIsaenko et al, , 2009bMalkin et al, 2001;Mel'nikova et al, 2005;Merkulov et al, 2005;Neukum et al, 1994;Nostrand et al, 2001;Okhrimchuk et al, 2006;Popova et al, 2001;Quagliano et al, 1996;Ren et al, 2003;Singh et al, 2005;Velázquez et al, 2006aVelázquez et al, , 2006bVirey et al, 1998;Vtyurin et al, 2004Vtyurin et al, , 2006. (*) per lead type of crystallographic site.…”

“…In order to understand by which mechanism(s), likely to affect population inversion kinetics during laser operation, all these levels gets populated in spite of the fact that excitation around 800 nm is non resonant, it proved useful to get excitation spectra of these emissions as well as fluorescence decay measurements under pulsed non resonant excitation. References Ferrier et al, 2007Ferrier et al, , 2008aQuimby et al, 2008;Tkachuk et al, 2007] highlight the relevance of such processes as :…”