Amorphous oxide interference coatings for multi-gigashot lifetime for inertial fusion energy laser drivers

The demonstration of fusion ignition at the National Ignition Facility at Lawrence Livermore National Laboratory in December 2022 is a key milestone towards the implementation of Inertial Fusion Energy (IFE) as an inexhaustible source of clean energy. This remarkable achievement sets a path to fusion power plants in which new high repetition rate IFE laser drivers will be needed to make laser fusion practical. Different IFE driver architectures could be used for laser fusion. However, in all of these systems the ability to operate at high energy, with high average power (high repetition rate) over multi-giga-shots exposure is in part limited by the damage of coatings in critical beam transport and focusing optics. How we propose to address the problem/ situation in Phase I: XUV Lasers Inc. in collaboration with Colorado State University proposes to address the scaling in the laser damage resistance of coatings for an operational wavelength ? =355 nm; nominal pulse duration <10 nsec, through an investigation of novel amorphous oxide materials for transmissive and reflective coatings. The innovative aspects of the proposed research will be: i) in the use of amorphous oxide mixtures and nanolaminate structures deposited by sputtering which will substitute the more-prone to damage layers in the coating; and ii) in tailoring the substrate/coating interface, which plays a critical role in the coatings’ adhesion and laser damage, to enhance their lifetime. Experiments to test laser damage resistance at ? = 355 nm, with a pulse duration of ~10 ns, and over multi-shot exposure will allow us to identify the most promising coating materials and coating architectures. Commercial applications and other benefits: The knowledge developed through this project will impact the engineering of interference coatings based on amorphous oxides for applications in IFE lasers in particular and broadly for high intensity lasers being used in large and medium frame DoE laser facilities.