ABSORPTION AND LUMINESCENCE SPECTROSCOPY OF CR4-DOPED CA2GEO4 - A POTENTIAL NEAR-INFRARED LASER MATERIAL()

Near infrared (NIR) absorption and luminescence experiments on Cr4+-do ped Ca2GeO4 single crystals are reported. In the absorption spectra th ree transitions from the (3)A(2) ground state to the three orbital com ponents of the T-3(2) excited state are observed. The luminescence tra nsition is from the lowest of these three orbital components to the gr ound state. Although the luminescence transition is spin allowed it is characterized by an unusually small Huang-Rhys factor. The luminescen ce of Cr4+-doped Ca2GeO4 is considerably less quenched at 275 K than t he luminescence of the well-known NIR laser material Cr4+-doped forste rite.