Thermal Analysis of Direct-Liquid-Cooled End-Pumped Nd:YLF Thin-Disk Lasers
Direct liquid-cooled end-pumped thin-disk lasers,which offer high output potential for beam quality,were analyzed focusing on addressing thermally induced wavefront distortion issues.A hydrodynamic laminar flow model was utilized for this purpose.Comparing the temperature distributions and wavefront distortions under two thermal loading conditions ideal full aperture pumping and less-than-ideal nonfull aperture pumping-revealed that heat accumulation within the coolant along the flow direction causes wavefront distortion along the same direction.In additional,a sharp decrease in temperature at the pumping edge position along the transverse direction of the thin-disk leads to considerable deterioration in the laser wavefront.Experimental results corroborate these findings.Furthermore,our thermal safety assessment highlights that the maximum thermal load of a single thin-disk is constrained by thin-disk stress,which becomes the bottleneck before the temperature rise at the solid-liquid interface.The analysis of thermally induced wavefront distortion revealed that the thermal deformation of the Nd∶YLF thin-disk has a minimal effect on wavefront distortion and the primary source of wavefront distortion is the fluid thermo-optic effect.