Abstract
We have examined how three different cleaning processes affect the laser-induced damage threshold (LIDT) of antireflection coatings for large dimension, Z-Backlighter laser optics at Sandia National Laboratories. Laser damage thresholds were measured after the coatings were created, and again 4 months later to determine which cleaning processes were most effective. Coatings that received cleaning exhibited the highest LIDTs compared to coatings that were not cleaned. In some cases, there is nearly a twofold increase in the LIDT between the cleaned and uncleaned coatings (19.4 J/cm2 compared to 39.1 J/cm2). Higher LIDTs were realized after 4 months of aging. The most effective cleaning process involved washing the coated surface with mild detergent, and then soaking the optic in a mixture of ethyl alcohol and deionized water. Also, the laser damage results indicate that the presence of nonpropagating (NP) damage sites dominates the LIDTs of almost every optic, despite the cleaning process used. NP damage sites can be attributed to defects such as nodules in the coating or surface contamination, which suggests that pursuing further improvements to the deposition or cleaning processes are worthwhile to achieve even higher LIDTs.
Highlights
The cleaning of optically polished substrates for optical coating purposes commands significant interest from scientists and engineers dealing with optics and lasers, as is evident from scholarly treatises[1,2,3,4,5] that address this topic in chapters or special sections
This confirms the importance of the final cleaning in achieving the highest laser-induced damage threshold (LIDT), and indicates that the DI water/alcohol soak can be effective as a final cleaning option
Each final cleaning method tested in this study resulted, on average, in higher LIDTs compared to no final cleaning of an AR coating
Summary
Other cleaning methods involve the use of acids or piranha Because these chemicals are known to attack optical coatings, they are most appropriate for cleaning more durable, uncoated substrate surfaces and should be used only with extreme care on coated surfaces so as not to damage the coatings. These published sources of information[1,2,3,4,5,6] are very helpful and informative but, along with presenting standard cleaning protocols and precautions, they all emphasize that optics cleaning is both a science and an art, and an optic or coating is “clean” as long as it is good enough (a) for subsequent processing or (b) to ensure its reliability for its intended use. The cleaning of optics and coatings is multifaceted, as are their applications, and sorting through standard protocols to arrive at effective cleaning methods for specific optics and purposes is very much a trial-and-error process governed by whether the optics or coatings meet the specifications of their particular uses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
