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Since its invention in 1974, atomic layer deposition (ALD) has shown tremendous performance in depositing thin film structures for various applications in physical, chemical, biological and medical sciences. The unique layer-by-layer growth mechanism of ALD enables exceptional uniformity, conformality and accurate control of film thickness for a plethora of materials. In physical sciences, especially in optical systems, these properties are of utmost importance as sustaining optical performance not only requires a high degree of uniformity, but also excellent conformality when it comes to complex micro- or macrostructures. To reach a high level of uniformity and conformality on complex macro shapes, such as highly curved lenses or spherical domes, effort needs to be made to specifically twist, turn, rotate or otherwise move the structures. For the traditional physical vapor deposition, this comes with an extensive load of mechanical work and process optimization, ultimately leading to a tight control of the process parameters. In the end, the optimized processes may still not lead to a sufficiently homogeneous film deposition on the most challenging structures. In this work, we demonstrate that we have been able to overcome these constraints by utilizing our P-series ALD batch tools to deposit various optical coatings on complex 3D macrostructures. As example structures, we use a topless cube (length, height, width = 150 mm) and a hemispherical dome (diameter = 155 mm). By depositing various low-loss oxide materials (SiO2, Al2O3, HfO2, TiO2 and Ta2O5) and by measuring their resulting thickness distributions from various locations throughout the 3D bodies, we have been able to achieve non-uniformities ranging from less than 1 % to 2.5 % over the entire structures. In addition, we have designed and deposited anti-reflective, highly reflective and edge-pass coatings on these structures and verified that excellent spectral responses from 400 to 2500 nm can be obtained. Ultimately, our results demonstrate an exceptional method to realize high-quality optical coatings on the most challenging surfaces, paving the way for the mass production of critical optical components in macroscale for a variety of applications ranging from military to microscopy.
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