Fig. 1. (a), (b) Calculated temperature distributions and (c), (d) axial displacement fields corresponding to AE on flat (a), (c) and profiled (b), (d) heatsinks at absorbed pump power of 100 W and element thickness of 800 μm. (e) Pump and heatsink profile for calculations. (f) Calculated change of the optical path corresponding to geometries (a) and (c) at 100 W pump power.

Fig. 2. (a) Photo of the profiled heatsink, (b) the active element and heatsink in the holder and (c) diagram of the experimental setup for measuring signal wavefront distortions in the active element under pumping. The scheme includes a system for pumping and cooling of the active element (laser head), as well as a Michelson interferometer for phase-shift interferometry.

Fig. 3. (a) Radial distribution of the pump profile in the active element, three variants of different sizes, obtained during the experiment. The curves indicate the dependence of power density on the radial coordinate, where the colors correspond to different sizes and the graphs are normalized to 1 W. (b) Measured dependence of the thermal lens on pump power corresponding to different sizes of the pump spot with profiled and flat heatsinks.

Fig. 4. Two-dimensional distribution of wavefront distortions in the AE, pump size 1.87 mm full width at half maximum (FWHM): (a), (b) on a profiled heatsink at 0 and 100 W pump power; (c), (d) on a flat heatsink. The red circle marks the area within which the approximation is made. The diameter of the red circle is 3.3 mm, while the diameter of the entire depicted area is 6.6 mm; the color scale is in micrometers.

Fig. 5. The influence of thermally induced wavefront distortions on probe beam quality: (a) deviation of the overlap integral from unity; (b) value of M². The diameter of the probe beam is plotted along the abscissa. ‘Experiment’ means that the distortion has been measured and the presented value is calculated based on this; ‘model’ means that both the distortion and the presented value have been calculated.

Fig. 6. (a) Layout of the laser amplifier with the disk AE, including the laser head with pump injection system and cooling, and a multipass signal amplification scheme. (b) Output pulse energy versus pump pulse energy. (c) Pump density distribution along the radial coordinate, and the heatsink profile used in this amplification scheme.

Fig. 7. Thermal lens strength and temperature of the AE surface versus average pump power. The lens strength was measured by two methods.