Crystalline structure and optical spectroscopy of Er3+-doped KGd(WO4)2 single crystals

KGd(WO4)(2) single crystals doped with Er3+ have been grown by the flux top-seeded-solution growth method. The crystallographic structure of the lattice has been refined, being the lattice constants a = 10.652(4), b = 10.374(6), c = 7.582(2) Angstrom, beta = 130.80(2)degrees The refractive index dispersion of the host has been measured in the 350-1500 nm range. The optical absorption and photoluminescence properties of Er3+ have been characterised in the 5-300 K temperature range. At 5 K, the absorption and emission bands show the (2J + 1)/2 multiplet splittings expected for the C-2 symmetry site of Er in the Gd site. The energy positions and halfwidths of the 72 sublevels observed have been tabulated as well as the cross sections of the different multiplets. Six emission band sets have been observed under excitation of the F-4(7/2) multiplet. The Judd-Ofelt (JO) parameters of Er3+ in KGW have been calculated: Omega(2) = 8.90 x 10(-20) cm(2), Omega(4) = 0.96 x 10(-20) cm(2), Omega(6) = 0.82 x 10(-20) cm(2). Lifetimes of the S-4(3/2), F-4(9/2), and I-4(11/2) multiplets have been measured in the 5-300 K range of temperature and compared with those calculated from the JO theory. A reduction of the S-4(3/2) and I-4(11/2) measured lifetimes with increasing erbium concentration has been observed, moreover the presence of multiphonon non-radiative processes is inferred from the temperature dependence of the lifetimes.