The crystal chemistry of the Sm³⁺ to Sm²⁺ reduction in tetraborate lattices was investigated. In crystalline SrB₄O₇ in air it is mainly Sm²⁺ that is incorporated from a melt or glass containing predominantly Sm³⁺. For the process in air, a reduction and pick-up mechanism is assumed to take place at the crystal/nutrient interface. Stabilization of Sm²⁺ in SrB₄O₇ at high temperature and in an oxidizing atmosphere seems to be a particular property of the system, because no Sm²⁺ inclusion could be observed along the series MB₄O₇ (M = Ca, Ba, Cd, Pb), if similar reaction conditions were applied. So far, there is only one other oxide lattice (BaB₈O₁₃) known where at high temperatures significant amounts of Sm²⁺ are obtained for reactions in the air.Single crystals of SrB₄O₇ : Sm²⁺ were grown by the Czochralski method (k_eff for Sm is 0.5). Optical hole burning experiments for the transition ⁵D₁–⁷F₀ were performed at 80 K. A hole with a width of 0.21 cm^–1 and a depth of 5.25% was formed for the first time for Sm²⁺ in a borate crystal excited by the beam of a single frequency dye laser. A rather small inhomogeneous linewidth of 0.28 cm^–1 allowed the burning of a single hole only.

Persistent spectral hole burning was performed on the ⁷F₀–⁵D₁ transition of Sm²⁺ in thin films of SrFCl. Depending on the substrate and the growth conditions, a total hole depth between 47% and 70% was reached. The holes were Lorentzians of width 4(±0.3) cm^−1. The time evolution of the hole depth was studied. It is described by two exponentials: a short time decay (t₁ = 0.37 days) and a long time decay (t₂ = 20.4 days) with a 20% infinite time limit. One- and two-photon burning mechanisms act.

Multicomponent thin films with spectral hole burning capacity at room temperature were synthesized by using molecular beam and pulsed laser deposition techniques All materials were activated by Sm²⁺ in low-symmetry alkaline earth sites, the synthesis involved the control of ionic diffiision rate during multilayer growth and special reduction of Samarium. Enhancement of hole burning rate by 1-2 orders is obtained in nanocrystalline films as compared to bulk and microcrystalline materials New hypothetic mechanism involving the creation of Sm-defect (photochromic) centers is proposed for reversible photoburning.

The growth of thin films made from Samarium-doped alkaline earth fluoro halides (AEFH) of composition Sr_xCa_1−xFCl:Sm²⁺ (0 ⩽ x ⩽ 1) is presented and the possibilities are studied to increase significantly the inhomogeneous width of the Sm²⁺ optical zero phonon transitions. The best films were obtained when grown with a molecular beam deposition (MBD) method involving two separate molecular beams: one for the alkaline earth fluoride, the other one for the alkaline earth halide (Cl or Br). The results demonstrate that the double beam MBD technique employed is able to produce pure and mixed Matlockite films with targeted composition. The results of mainly optical studies of the samarium f–f transitions and of other complementary techniques are used to assess the composition and homogeneity of the films. With the aid of a model the composition dependence of the positions of specific optical f–f emission lines is established. Their inhomogeneous linewidth is compared with that of corresponding emission lines obtained from bulk samples of the same chemical composition. The linewidths of the films are only slightly larger (∼1.5–2 times). Thus, the film morphology cannot be exploited to increase substantially the inhomogeneous broadening of the luminescence lines. A novel approach to increase this broadening was devised, theoretically modeled and successfully tested by using multilayered sandwich-type thin films in conjunction with interdiffusion. Films with cation disorder of composition Sr_xCa_1−xFCl (x = 0.5 /0/ 0.5/ 0/..) were grown. The ⁵D₁→⁷F₀ Sm²⁺ emission linewidth is thereby increased to 70 cm^−1 full width half maximum. A width of 100cm^−1 may be obtained within the composition range x = 0, x = 1. This represents an enhancement by a factor of 3–5 in comparison with the largest values obtained in appropriate mixed bulk AEFH of constant composition. A factor >50 is gained in comparison with pure bulk AEFH hosts. The room temperature (RT) homogeneous linewidths, on the other hand, are similar to those found in bulk mixed crystals of constant composition. The intrafilm host cation diffusion during film growth of the sandwich structures was further studied. A diffusion constant of 2â‹…10^−19m²s^−1 for the Sr and Ca ions was deduced from this observation. These films are among the most promising materials for optical mass data storage through RT hole-burning.

The results of a detailed optical and paramagnetic-resonance study performed on copper in CaF₂ and silver in BaF₂ are presented. Two different Ag⁺ centers were identified in BaF₂. One is associated with an interstitial F^- ion whereas the other one has a cubic surrounding. The Cu²⁺ ion in CaF₂ was shown to reorient at 4.2 K between 6 equivalent minima of D_2h symetry. This fact is interpreted with the aid of a T_2gx(T_2g+E_g) type Jahn-Teller effect. The nonlinear mixed coupling terms are shown to play an important role. The Cu⁺ impurity in CaF₂ is presumably off-center in the F^- sublattice without associated defect or impurity.

Optical hole burning, a potential technique for spectrally selective recording, was demonstrated in Sm-doped MBE-grown thin films of CaF₂/Si(111). The inhomogeneous broadening of the corresponding Sm²⁺ 5d(T_1u) ↞ 4f(⁷F₀, A_1g) transition (690 nm) was investigated as a function of substrate temperature and film thickness. The MBE apparatus is briefly described as well as the thin film growth procedure.

When modern spectral hole burning applications for high-density information storage under noncryogenic temperatures are envisioned, it is necessary to develop new frequency-selective photoactive materials for this purpose. Mixed compounds of the PbFCl family, doped with samarium(II) ions, exhibit promising and true room-temperature hole burning capabilities. We investigate this class of systems (and related ones) by combining material synthesis and high-resolution spectroscopy. Whole groups of isomorphous crystals were synthesized with varying degrees of halide anion and/or cation substitutions. Thin films of fluoride-based materials were made in a laboratory-built molecular beam epitaxy system. An extended x-ray study, differential thermal analysis, luminescence, and Raman measurements allowed the characterization of the materials. Formal models were developed for both the inhomogeneous zero-phonon optical line shapes of the samarium(II) and the time evolution of the hole burning.