Critical processing temperature for high-performance protected silver mirrors

David M. Fryauf; Andrew C. Phillips; Nobuhiko P. Kobayashi

doi:10.1117/1.JATIS.7.3.034002

28 July 2021 Critical processing temperature for high-performance protected silver mirrors

David M. Fryauf, Andrew C. Phillips, Nobuhiko P. Kobayashi

Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 7, Issue 3, 034002 (July 2021). https://doi.org/10.1117/1.JATIS.7.3.034002

Abstract

Silver (Ag) mirrors for astronomical telescopes consist of multiple metallic and dielectric thin films. Furthermore, the topmost surface of such Ag mirrors needs to be covered by a protection coating. While the protection coating is often deposited at room temperature and the entire mirrors are also handled at room temperature, various thin-film deposition techniques offer protection coatings with improved characteristics when carried out at elevated temperatures. Thus, high-performance Ag mirrors were designed and fabricated with a new benchmark. The resulting Ag mirrors were annealed (i.e., post-fabrication annealing) at various temperatures to investigate the viability of introducing thermal processes during and/or after fabrication in improving the overall optical performance and durability of protected silver mirrors. In our experiments, Ag mirror samples were deposited by electron-beam evaporation and subsequently annealed at various temperatures in the range from 60°C to 300°C, and then the mirror samples underwent an environmental stress test at 80°C and 80% humidity for 10 days. While all the mirror samples annealed below 200°C showed negligible corrosion after undergoing the stress testing, those annealed below 160°C presented spectral reflectivity comparable to or higher than that of as-deposited reference samples. In contrast, the mirror samples annealed above 200°C exhibited significant degradation after the stress testing. The comprehensive analysis indicated that delamination and voids caused by the growth of Ag grains during the annealing are the primary mechanisms of the degradation.

Citation Download Citation

David M. Fryauf, Andrew C. Phillips, and Nobuhiko P. Kobayashi "Critical processing temperature for high-performance protected silver mirrors," Journal of Astronomical Telescopes, Instruments, and Systems 7(3), 034002 (28 July 2021). https://doi.org/10.1117/1.JATIS.7.3.034002

Received: 18 March 2021; Accepted: 15 July 2021; Published: 28 July 2021

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available