A spectral hole burning study of BaFCl 0.5Br 0.5:Sm 2+

Abstract

Investigations of parameters for two-photon hole burning (single colour and photon-gated) and hole erasing in the three 4f 6 7F 0- 5D j electronic transitions in BaFCl 0.5Br 0.5:Sm 2+ are presented. This material is of particular interest as it has unusually large inhomogeneous zero-phonon line widths allowing holes to be burnt at relatively high temperatures. For the transition to the 5D 0 excited state, only photon-gated holes could be burnt whereas gating light-enhanced single-colour hole burning in the 5D 1 transition by a factor of about five. Gating light did not significantly increase the hole burning rate for the 5D 2 transition but did increase the resistance of the holes to erasing by irradiation from the gating beam alone. Such erasing during the burning process decreases the effective gating ratios for all transitions. The hole width burning power dependence was investigated, the minimum hole width at 1.8 K being 14 MHz. The temperature dependence of the 5D 2 hole width was investigated between 1.8 and 90 K, suggesting two regions. Below about 20 K the hole width dependence was found to be T 1.3 whilst above 20 K it was found to be T 2.9. A similar temperature dependence was found for the widths of holes burnt in the other two transitions in the high-temperature regime but the holes were generally broader below 20 K. This was attributed to the requirement of higher burn and read power densities. Holes could be burnt at temperatures up to 133 K and could be cycled from 1.8 K to room temperature, becoming much shallower in the process.