Spectroscopy of V4+ and V3+ ions in a forsterite crystal

The absorption spectra of impurity vanadium ions in forsterite crystals are studied in the wavelength range from 600 to 2000 nm. It is found that the V⁴⁺ ion in the tetrahedral coordination in crystals grown by the Czochralski technique exhibits strong absorption in the range from 600 to 1200 nm. The intense electron-vibrational progressions in the absorption spectra of impurity d-ions in crystals were observed for the first time at temperatures 300 and 77 K. In the authors' opinion, these progressions appear due to the formation of the oxovanadate complex and distortions of the structural tetrahedron. The forsterite crystal doped with V⁴⁺ ions has a very high absorption cross section (up to 2.1×10^–18 cm²) and a continuous broad absorption band, which makes this crystal promising as a passive laser switch in the range between 600 and 1200 nm. At the same time, the V⁴⁺ ions in the forsterite crystal do not emit luminescence because of a high probability of the nonradiative relaxation of their excited state. It is shown that luminescence of a V:Mg₂SiO₄ crystal is related to the tetrahedral V³⁺ ion.