Measurement of transmitted wavefront on highly pumped Yb:glass

Time resolve wavefront measurement was proved to clarify cooling process of the highly pumped ytterbium glass. A Shack-Hartmann sensor and a flashlamp pumped Ti:sapphire laser were used for wavefront measurement and high intensity pumping. Temporal change of focus and astigmatism are dominant in Zernike coefficients. Thermal lens of 1 m radius was found for the pumping intensity of 800 kW/cm2. Temporal decay of thermal lens effects on ytterbium glass agreed well with unsteady 1-D heat conduction. The wavefront distortion completely disappears within the characteristic cooling time. The proposed technique here can be applied to develop the effective cooling method for highly pumped gain media. (author)