Abstract

The rapid advance of high-power CO₂ laser systems is urgently calling the innovation of laser beam reflectors with a high laser-induced damage threshold (LIDT) above 10000 W/cm² for their stable operation in extreme conditions. In this work, we integrated a 3D-printed copper water-cooling system (laser powder bed fusion fabricated) with a multilayer coating technique to promote the LIDT of 10.6 μm reflectors, surface modification using electron beam evaporation ion beam assisted deposition (IAD) of Cu films, and 10.6 μm reflective films of 3251 nm in thickness (800 nm-Ge/699 nm-ZnS/779 nm-Ge/863 nm-ZnS/100 nm-Au/10 nm-Cr).

After integration of a water-cooling system, the surface temperature upon of 5093 W/cm² drops 53% (45.00 °C vs. 84.20 °C) and the LIDT increased by 60% (8488 ± 127 to 13581 ± 203 W/cm2), demonstrating a performance enhancement while reflectance of >99.50% at 45°. Cu-modified layer’s high thermal conductivity (401 W/(m·K)) suppresses thermal accumulation, thermal deformation peak-to-valley falls from 12292 nm (1.16 λ) to 3082 nm (0.29 λ). While keeping the reflective multi-layer and just changing of the 1st-layer coating, Cu-modified layer is found to exhibit superior thermal dissipation properties over Ni-modified layer.

This work is instructive regarding for realizing better thermal control of reflectors for high-power laser-containing high-end equipment such as EUV lithography.