Influence of Sm3+-Ions on the Hole-Burning Efficiency of Sm2+-Ions Doped in Mg0.5Sr0.5FCl0.5Br0.5 Mixed Crystals

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Sm-doped Mg0.5Sr0.5FCl0.5Br0.5 mixed crystals were prepared by three different methods and their optical properties were studied through emission spectroscopy and the hole-burning technique. While the sample prepared in air (MA) shows the transition lines due to Sm3+-ions, the sample prepared in hydrogen (MH) shows Sm2+ emission lines. We could also observe the reduction effects of Sm3+ in the X-ray irradiated sample (MX). The spectral holes were burnt within the 7F0–5D1 transition band and the hole-burning efficiencies in the MH and MX samples were measured at room temperature and 9 K, using the one color and two color hole-burning techniques. The hole-burning efficiency decreased with the lowering of the temperature, and almost no hole signal was found at 9 K in the MX sample. We thus performed a site selective excitation experiment to reveal the origin of the decrease of hole-burning efficiency with decreasing temperature. On the basis of these results, we found that the energy used to excite the Sm2+-ions in the hole-burning process is also simultaneously used to excite the residual (or unreduced) Sm3+-ions, and we also found that the excitation efficiency of the Sm3+, compared to that of Sm2+, increased with decreasing temperature. As a result, we consider that the residual Sm3+-ions strongly affect the hole-burning efficiency and the photoluminescence properties of the Sm2+ by depriving the Sm2+-ions of excitation energy.
2004-12-15