Device for measuring of thermal lens parameters in laser active elements with a probe beam method

We have developed a device for measuring of parameters of thermal lens ( TL) in laser active elements under longitudinal diode pumping. The measurements are based on the probe beam method. This device allows one to determine sign and optical power of the lens in the principal meridional planes, its sensitivity factor with respect to the absorbed pump power and astigmatism degree, fractional heat loading which make it possible to estimate integral impact of the photoelastic effect to the formation of TL in the laser element. The measurements are performed in a linearly polarized light at the wavelength of 532 nm. Pumping of the laser element is performed at 960 nm that makes it possible to study laser materials doped with Yb3+ and ( Er3+, Yb3+) ions. The precision of measurements: for sensitivity factor of TL -0,1 m(-1)/W, for astigmatism degree -0,2 m(-1)/W, for fractional heat loading -5 %, for the impact of the photoelastic effect -0,5 x 10(-6) K-1. This device is used for characterization of thermal lens in the laser active element from an yttrium vanadate crystal, Er3+, Yb3+: YVO4.