Thermo-optical effects in diode end-pumped Yb-doped laser crystals and sesquioxide ceramics.
In this work we experimentally determined values of focal length for thermal lenses in diode end-pumped Yb3+ : YVO4, Yb3+ :  Gd0.64Y0.36VO4 crystals and Yb3+ : Y2O3, Yb3+ : Sc2O3 laser ceramics. A chosen method for determination of thermal lens in solid state laser media as a function of pump power was based on measurement of a focal point displacement. In theoretical calculations of focal length of thermal lens we took into account effects of temperature and stress-dependent variations of the refractive index and distortion end faces of crystal. Data of focal lengths for thermal lenses in vanadate crystals and Yb : Y2O3, Yb : Sc2O3 ceramics were obtained for the first time. Results were used for creation of terawatt femtosecond laser system with a repetition rate of 1 kHz.