Broadband absorption coating for large-curvature surfaces by atomic layer deposition.

For many applications, large curvature surfaces or complicated 3D structures are required to absorb light that falls on them to reduce stray light or energy collection. A novel, to the best of our knowledge, strategy with a metal-dielectric film stack by the atomic layer deposition technique is put forward to achieve broadband absorption coating covering both sides of a quartz tube completely. Absorptive metallic material of titanium-aluminum-carbon composite and dielectric material of aluminum oxide (Al2O3) is employed to realize high absorption (>99%) for the 400-780 nm band with the configuration of a six-layer metal-dielectric film stack. Good angle insensitivity up to 50° for P- and S-polarizations is demonstrated experimentally with the proposed structure on a glass slab. The average absorption of the coated quartz tube reaches as high as 99% for all curving areas on the inner and outer sides, while the nonuniformity is confined to 1.5% for the axial and circumferential directions. This presented approach has enormous potential in the fields of optical detection, optical imaging, optical sensing, and energy management.