Laser-induced pit formation in UV-antireflective coatings

S. Paschel; I. Balasa; L. O. Jensen; X. Cheng; Z. Wang; D. Ristau

doi:10.1117/12.2500338

16 November 2018 Laser-induced pit formation in UV-antireflective coatings

S. Paschel, I. Balasa, L. O. Jensen, X. Cheng, Z. Wang, D. Ristau

Proceedings Volume 10805, Laser-Induced Damage in Optical Materials 2018: 50th Anniversary Conference; 108051N (2018) https://doi.org/10.1117/12.2500338
Event: SPIE Laser Damage, 2018, Boulder, Colorado, United States

Abstract

Previous studies have shown that nanometer scale defects can lead to the formation of submicrometer craters, if located in coatings with a relatively small thickness. Due to the small size, such damages are challenging to detect in the online and offline damage detection and may therefore lead to an overestimation of the LIDT for the tested optical component. However, the influence of these nanopits on the optical properties and the impact on the initiation of catastrophic damage was not investigated in detail in the past. In order to study the correlation between nanopits, optical properties and catastrophic damage, samples with an AR-coating were fabricated by means of ion beam sputtering (IBS) and tested for their laser resistance by LIDT raster scans in the nanosecond regime at 355 nm. The generation and morphology changes of the nanopits were monitored for different pulse numbers and in dependence of the starting fluence. In addition to the inspection with an optical microscope in differential interference contrast (DIC) mode as prescribed by ISO 21254, alternative inspection methods, for example, dark field microscopy and scanning electron microscopy (SEM), were used to detect the nanopits. The damage test revealed that nanopits occur rarely in standard AR-coatings and possess only a small relevance for the LIDT. The typical damage morphology observed consisted of micrometer-sized pits which exhibited a stable size over a large fluence range and no growth after repeated irradiation.

Citation Download Citation

S. Paschel, I. Balasa, L. O. Jensen, X. Cheng, Z. Wang, and D. Ristau "Laser-induced pit formation in UV-antireflective coatings", Proc. SPIE 10805, Laser-Induced Damage in Optical Materials 2018: 50th Anniversary Conference, 108051N (16 November 2018); https://doi.org/10.1117/12.2500338

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