Thermo-optical parameters and dispersion of pure and Yb(3+)-doped KY(WO4)2 laser crystals

Dispersion of the principal refractive indices of pure and Yb(3+) (20 at.%)-doped KY(WO(4))(2) crystal is obtained in the visible range of the spectrum. A comparatively strong increase of the refractive indices (0.005-0.007) was observed for the doped crystal. Temperature dependence of the principal refractive indices is measured in the temperature region of 290-690 K. Thermo-optical coefficients (TOCs) of the first dn/dt and the second (1/2)(d(2)n/dT(2)) order are determined. It is found that TOCs are negative for n(p) and n(g) and positive for n(m) in both crystals. Doping increases dn(p)/dT almost two times more in comparison to that of the pure crystal, while for the other two indices TOC changes are insignificant.