UP-CONVERTED LUMINESCENCE AND EXCITED-STATE EXCITATION SPECTROSCOPY OF CR4+ IONS IN FORSTERITE

The electronic structure of Cr4+-doped forsterite is studied using up-converted luminescence and excited-state excitation spectroscopy. Two metastable states with energies higher than the energy of the T-3(2) lasing level are identified. The first, higher-lying state was identified as T-3(1)(t(2)e) electronic state. Three lines were resolved at 26 424, 26 529, and 26 625 cm(-1), corresponding to the spin-orbit-split zero-phonon line of the T-3(1)(t(2)e) state. The lifetime of this state was measured to be 395 ps. The second, lower-lying state is located at 12 847+/-90 cm(-1) and is assigned to the T-3(1)(t(2)(2)) state. Its lifetime is estimated to be of the order of a few hundred nanoseconds.