High-Uniformity Ultra-Broadband Composite Coatings for Large-Aperture Space Telescopes Using Dual-Ring Co-Evaporation

In addressing the key technical challenges of achieving ultra-broadband and high film-thickness uniformity for meter-class large-aperture space telescopes, this study utilized a self-developed 4 m-class large-aperture thin-film deposition system. By employing plasma-assisted electron-beam evaporation technology and a co-evaporation method with inner and outer dual-ring multi-evaporation sources, precise control of film-thickness uniformity within a 2 m range was achieved. A composite film structure combining a metal reflective layer and an ultraviolet-enhanced dielectric layer was adopted to realize high reflectivity across an ultra-broad spectrum from ultraviolet to long-wave infrared. Experimental results show that the average reflectance of the composite film reaches 91.52% in the 0.25~0.38 μm spectral band and 99.40% in the 0.38~12 μm spectral band. The thickness uniformity of ZrO2 and MgF2 films within the 2 m aperture area was controlled at 1.37% and 3.12%, respectively, meeting the requirements for high uniformity in large-aperture space applications. Radiation testing confirmed that the change in film reflectance is less than 1% under a total irradiation dose of 3.66 × 108 rad(Si), satisfying the demands for operation in harsh space environments. This research provides an innovative solution for thin-film technology in large-aperture, ultra-broad-spectrum space optical systems and holds significant value for engineering applications.