Thermo-optic characterization of Yb:YAl3(BO3)4 laser crystal

Principal thermo-optic coefficients, dn o/dT and dn e/dT, are determined for 7at.%Yb: YAl3(BO3)4 crystal by the use of a minimum deviation method, modified for anisotropic, optically uniaxial crystals. Direct measurements are accompanied by modeling of the dn/dT versus light wavelength dependence, yielding analytic thermo-optic dispersion formulae for the spectral range of 0.4–1.6 μm. At the wavelength of 1030 nm, dn o/dT = 3.5 and dn e/dT = 6.0 [10−6 K−1]. Sellmeier formulas are evaluated for the principal refractive indices n o and n e. The thermal coefficients of the optical path are determined for the principal crystal cuts of Yb:YAl3(BO3)4, a-cut and c-cut, and light polarizations, π or σ. Finally, thermal lens parameters are evaluated for Yb:YAl3(BO3)4 crystals on the basis of measured material parameters.