Impact of high-temperature annealing on hafnia-silica composite coatings deposited via ion beam sputtering for high-peak power 1064 nm lasers

Journal Article · Thu Sep 25 04:00:00 EDT 2025 · Optical Materials Express

DOI:https://doi.org/10.1364/OME.572003· OSTI ID:2997576

Harthcock, Colin ^[1]; Nguyen, Hoang T. ^[1]; Vipin, D. ^[2]; Huang, M. ^[2]

---

1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
2. SUNY Polytechnic Institute, Albany, NY (United States)

The maximum power handling fluence of high-peak and average power laser systems is often limited by the laser damage of the coatings on optical components. Furthermore, these multilayer dielectric coatings are limited in their maximum power handling due to laser-damage-prone defects in the lower optical bandgap, higher optical index material. Some of these defects can be mitigated by thermal annealing to high temperatures, which can greatly reduce the linear absorbative precursors. Typically, hafnia and silica are the materials of choice for high-peak and average power laser systems in the ultraviolet through infrared spectral range; however, hafnia crystalizes readily when annealed at high temperatures. In this study, we prepare composite HfO₂-SiO₂ coatings by co-sputtering hafnia and silica in an ion beam sputtering system and compare them to pure hafnia-based coatings. We demonstrate that crystallinity in hafnia can be completely suppressed when it is mixed with silica, such as the composite coatings in this study. High reflectors were fabricated and annealed, demonstrating that the multilayer dielectric stacks can survive high-temperature annealing and exhibit an excellent linear absorption of 0.2 +/- 1 ppm at 1064 nm. Short- and long-pulse laser damage was explored, demonstrating the complex relationship between linear absorption and the non-linear absorption which drives pulsed laser damage. These results provide an excellent route to the creation of very low linear absorption optical coatings, which also utilize low scattering materials that are best suited for high-peak and average power applications.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 2997576
• Report Number(s): LLNL--JRNL-2007146
• Journal Information: Optical Materials Express, Journal Name: Optical Materials Express Journal Issue: 10 Vol. 15; ISSN 2159-3930
• Publisher: Optica Publishing Group
• Country of Publication: United States
• Language: English