| Autor: |
James B. Oliver, A. Shvydky, Brendan T. Marozas, Semyon Papernov, A. A. Kozlov, Terrance J. Kessler |
| Rok vydání: |
2014 |
| Předmět: |
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| Zdroj: |
Optical Engineering. 53:122504 |
| ISSN: |
0091-3286 |
| DOI: |
10.1117/1.oe.53.12.122504 |
| Popis: |
Hafnium oxide (HfO2) is the most frequently used high-index material in multilayer thin-film coatings for high-power laser applications ranging from near-infrared to near-ultraviolet (UV). Absorption in this high-index material is also known to be responsible for nanosecond-pulse laser-damage initiation in multilayers. In this work, modification of the near-UV absorption of HfO2 monolayer films subjected to irradiation by continuous-wave (cw), 355-nm or 351-nm laser light focused to produce power densities of the order of ∼100 kW/cm2 is studied. Up to a 70% reduction in absorption is found in the areas subjected to irradiation. Temporal behavior of absorption is characterized by a rapid initial drop on the few-tens-of-seconds time scale, followed by a longer-term decline to a steady-state level. Absorption maps generated by photothermal heterodyne imaging confirm the permanent character of the observed effect. Nanosecond-pulse, 351-nm and 600-fs, 1053-nm laser-damage tests performed on these cw laser–irradiated areas confirm a reduction of absorption by measuring up to 25% higher damage thresholds. We discuss possible mechanisms responsible for near-UV absorption annealing and damage-threshold improvement resulting from irradiation by near-UV cw laser light. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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