Impact of contamination and aging effects on the long-term laser damage resistance of SiO2/HfO2/TiO2 high reflection coatings for 1054 nm

Abstract

The laser damage thresholds of optical coatings can degrade over time due to a variety of factors, including contamination and aging. Optical coatings deposited using electron beam evaporation are particularly susceptible to degradation due to their porous structure. In a previous study, the laser damage thresholds of optical coatings were reduced by roughly a factor of 2 from the years 2013 to 2017. The coatings in question were high reflectors for 1054 nm that contained SiO 2 and HfO 2 and/or TiO 2 layers, and they were stored in sealed PETG containers in a class 100 clean room with temperature control. At the time, it was not certain whether contamination or thin-film aging effects were responsible for the reduced laser damage thresholds. Therefore, to better understand the role of contamination, the coatings were recleaned and the laser damage thresholds were measured again in 2018. The results indicate that the contamination played the most dominant role in reducing the laser damage thresholds of these optical coatings, even though they were stored in an environment that was presumed to be clean. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Analysis of laser-induced contamination at 515 nm in the sub-ps/MHz regime

“…Other studies were also conducted in the context of high power laser facilities for fusion experiments, also dealing with molecular contamination under exposure to nanosecond UV lasers. [35][36][37][38] In that case, the repetition rate is very low and the number of laser shots is very limited. Ex situ diagnostics such as Nomarski Microscopy, Confocal Fluorescence Microscopy (CLSM), White Light Interferometry (WLIM), Atomic Force Microscopy (AFM) are the most relevant tools of investigation.…”

Investigation of laser-induced contamination on dielectric thin films in MHz sub-ps regime

“…To simulate space conditions, a high vacuum chamber is utilized, and contamination growth is regulated by introducing a selected contaminant into the chamber. Studies on molecular contamination under nanosecond UV laser irradiation have also been undertaken in high-power laser facilities specialized in fusion research, such as those described in references (Bien-Aimé et al, 2009;Favrat et al, 2014;Field and Kletecka, 2019). However, the highly powerful pulses emitted by these facilities have a very low repetition rate, which limits the total number of laser pulses used in experiments.…”

Sub-ps MHz green laser-induced contamination on dielectric coatings in air

“…Studies on molecular contamination under nanosecond UV laser irradiation were also undertaken in high-power laser facilities specialized on fusion research. [30][31][32][33] In these facilities, the highly powerful pulses are emitted with a very low repetition rate, limiting the total number of laser pulses used in experiments.…”