Strategy to improve the long-term stability of low-stress e-beam coatings

The performance of the electron-beam (e-beam) coatings can be easily affected by the environmental humidity due to their porous nature. We propose a shell layer strategy deposited by plasma ion-assisted deposition to cover the top surface and sidewall of the e-beam coating. The long-term optical and mechanical stability of the prepared multilayer coatings with and without the shell layer are compared. Our results show that the shell layer strategy can effectively isolate the underlying e-beam coating from the ambient humidity, thereby significantly improving the long-term stability and mechanical properties of the e-beam coating. Meantime, the shell layer strategy of isolating ambient humidity avoids the increase in compressive stress caused by water absorption of the e-beam coating, thereby keeping the entire coating stress at a low level. The proposed shell layer strategy can be used to address the time- and environment-dependent instability issues of the e-beam coatings for high-power laser applications. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement