Temporal change of thermal lens effects on highly pumped ytterbium glass by wavefront measurement

The temporal change of thermal lens effects has been measured for the development of high efficient laser system. Ytterbium phosphate glass was used due to its high saturation fluence property. A free running flashlamp pumped Ti : sapphire laser was developed for the high energy pump source. Pumping intensity on the glass surface exceeded 800 kW/cm2 which is enough high for laser diode simulator. Shack-Hartmann wavefront sensor system was applied to measure the thermal lens effects on a highly pumped ytterbium glass oscillator. The temporal change of wavefront was successfully measured at high repetition rate of 100 Hz. The measured wavefront were expanded to Zernike coefficients. Cooling process for the focus coefficient agreed well with the prediction of unsteady one dimensional heat conduction. (author)