Charge Compensation of Er3+ Ions in Ca1—xErxF2+x Thin Films at Low Rare-Earth Substitution Rates

Concentration dependence of the Judd–Ofelt parameters of Er3 +ions in CaF2crystals

“…The last emission band, not reported earlier, appears strong only for two samples (samples 4 and 6). The other emission bands were observed by many authors [18,21]. The emission intensity depends on the concentration.…”

“…This can be related to the fact that in the range of the investigated concentrations, the same charge compensation mechanisms appear. The charge compensation is obtained by F − ions in various interstitial positions, which correspond to C 4v (NN) or C 3v (NNN) site symmetry [18,25]; the O h cubic symmetry (without charge compensator close to the Er 3+ ions) is less probable as the concentration increases.…”

“…The RE-doped low-phonon crystals, such as fluorides, are well known as materials for LD-pumped VIS lasers, IR lasers for medical applications, energy upconversion, etc. The laser performance of the Er 3+ :CaF 2 system has been studied by various authors [11][12][13][14][15][16][17][18][19][20][21]. Although the CaF 2 crystal is known as a good laser host, the J-O analysis of the Er 3+ ions in this host has been less investigated, mainly for IR emission [8,22].…”

Effective segregation coefficient of Er3+ions in ErF3-doped CaF2crystals

“…If the crystals are grown in reducing conditions with an excess of fluorine the predominant dipolar complex is one of tetragonal (C 4v ) symmetry in which the F − i occupies a nearest-neighbor (NN) interstitial site. Besides the tetragonal (C 4v ) symmetry, many other simple configurations may appear, such as O h (no local charge compensation), trigonal (C 3v ) symmetry or cluster configurations, as the RE ions concentration increases [2,3,18,19]. Such a complicated structure leads in turn to optical transitions having the form of broad and structured bands, as the peak corresponding to the 4 I 15/2 -4 I 13/2 transition.…”

“…The homogeneous distribution of the impurity in laser crystals is important because this affects the efficiency of the laser. Although these crystals are known as a good laser host [1][2][3][4][5], surprisingly, an analysis of the Er 3+ ions distribution along the CaF 2 crystal has not been reported so far. The only one reported value of the effective segregation coefficient, k eff , for Er 3+ in the CaF 2 host is 0.93 [6], determined in quaternary (Er 3+ , Yb 3+ , Ce 3+ , Na + ) doped CaF 2 .…”