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Optical Engineering • Open Access

Near-ultraviolet absorption annealing in hafnium oxide thin films subjected to continuous-wave laser radiation
Author(s): Semyon Papernov; Alexei A. Kozlov; James B. Oliver; Terrance J. Kessler; Alexander Shvydky; Brendan T. Marozas

Paper Abstract

Hafnium oxide (HfO 2 ) 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 HfO 2 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/cm 2 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.

Paper Details

Date Published: 25 June 2014
PDF: 6 pages
Opt. Eng. 53(12) 122504 doi: 10.1117/1.OE.53.12.122504
Published in: Optical Engineering Volume 53, Issue 12
Show Author Affiliations
Semyon Papernov, Univ. of Rochester (United States)
Alexei A. Kozlov, Univ. of Rochester (United States)
James B. Oliver, Univ. of Rochester (United States)
Terrance J. Kessler, Univ. of Rochester (United States)
Alexander Shvydky, Univ. of Rochester (United States)
Brendan T. Marozas, Cornell Univ. (United States)

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