Photon gated spectral hole burning in SrTiO₃ : Cr³⁺

Persistent spectral holes were observed in the R-lines of SrTiO3+ at 2 K. The hole burning mechanism was shown to be due to a two-photon or gated process, where a second optical excitation causes bleaching by photoionization of Cr3+. The trapping center responsible for the hole burning is postulated to be an oxygen vacancy in the lattice associated with a Cr3+ ion. A series of samples reduced at different temperatures was studied, and the hole burning efficiency was seen to be strongly dependent on reduction temperature. © 1994.