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UNCLASSIFIED, PUBLIC RELEASE
Achieving Accuracy in Laser-Induced Damage Testing of Optical Materials
Noel De la Cruz*, Cassidy Feltenberger*, Daniel Martinez*, Chelsea Appleget**, James Barrie**
The study of laser-induced damage thresholds (LIDT) in optical materials requires a carefully controlled, application-specific experimental approach, as standardizations of irradiation methods and protocols, adaptation to component geometries, and even definitions of damage, continue to be proposed and refined [1]. LIDT testing is made further complex as advancements are made in optical coatings design and manufacturing and as modern high-energy laser applications trend towards increased peak fluence [2][3]. The combination results in a range of damage types (for example, thermal versus electric-field induced damage), as well as shift of the interrogation from the optical material itself to the thin film coating [4]. It is thus imperative to understand the nuances of LIDT testing and how to characterize optical materials to accurately predict the laser fluence they can withstand before the onset of damage. To this aim, researchers at The Aerospace Corporation are developing experimental testbeds for the determination of pulsed and continuous wave (CW) LIDT values of various optical materials and components. An overview of the current testbed development is presented, as well as a discussion on key parameters identified during testing, especially with regards to beam width measurement and control, as small changes in the testbed geometry can lead to considerable changes in assessed LIDT values. To illustrate these key variables, a damage threshold is presented for a selection of commercial off-the-shelf (COTS) mirrors when tested with a single shot, pulsed (2 nanosecond pulse width) 1064 nm wavelength source. We will discuss which improvements can be made to the testbed to control certain variables and lead to more efficient and accurate testing. The ultimate goal is to provide application-appropriate testing guidance to reliably measure and report accurate LIDT values for optical components.
*Photonics Technology Department, Physical Sciences Laboratories, The Aerospace Corp.
**Space Materials Laboratory, Physical Sciences Laboratories, The Aerospace Corp.
References
[1] A. Melninkaitis, M. Keršys, et. al., "Progress in standardizing laser-induced damage threshold testing", Proc. SPIE 13190, Laser-Induced Damage in Optical Materials 2024, 1319009 (17 December 2024); https://doi.org/10.1117/12.3029899
[2] J. Nilsson, J. Sahu, Y. Jeong, et. al., "High-power fiber lasers: new developments", Proc. SPIE 4974, Advances in Fiber Lasers, (3 July 2003); https://doi.org/10.1117/12.478310
[3] E. Sistrunk, D. A. Alessi, et. al., "Laser Technology Development for High Peak Power Lasers Achieving Kilowatt Average Power and Beyond", Proc. SPIE 11034, Short-pulse High-energy Lasers and Ultrafast Optical Technologies, 1103407 (26 April 2019); https://doi.org/10.1117/12.2525380
[4] D. Ristau, M. Jupé, K.Starke, “Laser damage thresholds of optical coatings”, Thin Solid Films,
Volume 518, Issue 5, (31 December 2009), Pages 1607-1613, ISSN 0040-6090; https://doi.org/10.1016/j.tsf.2009.07.150
UNCLASSIFIED, PUBLIC RELEASE
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