PROCEEDINGS ARTICLE | December 2, 2010
Proc. SPIE. 7842, Laser-Induced Damage in Optical Materials: 2010
KEYWORDS: Reflectors, Laser induced damage, Laser energy, Physics, Optical testing, Laser damage threshold, Laser optics, Optical damage, Pulsed laser operation, Laser systems engineering
As high energy laser systems evolve towards higher energies, fundamental material properties such as the laserinduced
damage threshold (LIDT) of the optics limit the overall system performance. The Z-Backlighter Laser Facility
at Sandia National Laboratories uses a pair of such kiljoule-class Nd:Phosphate Glass lasers for x-ray radiography of
high energy density physics events on the Z-Accelerator. These two systems, the Z-Beamlet system operating at 527nm/
1ns and the Z-Petawatt system operating at 1054nm/ 0.5ps, can be combined for some experimental applications. In
these scenarios, dichroic beam combining optics and subsequent dual wavelength high reflectors will see a high fluence
from combined simultaneous laser exposure and may even see lingering effects when used for pump-probe
configurations. Only recently have researchers begun to explore such concerns, looking at individual and simultaneous
exposures of optics to 1064 and third harmonic 355nm light from Nd:YAG [1]. However, to our knowledge,
measurements of simultaneous and delayed dual wavelength damage thresholds on such optics have not been performed
for exposure to 1054nm and its second harmonic light, especially when the pulses are of disparate pulse duration.
The Z-Backlighter Facility has an instrumented damage tester setup to examine the issues of laser-induced
damage thresholds in a variety of such situations [2] . Using this damage tester, we have measured the LIDT of dual
wavelength high reflectors at 1054nm/0.5ps and 532nm/7ns, separately and spatially combined, both co-temporal and
delayed, with single and multiple exposures. We found that the LIDT of the sample at 1054nm/0.5ps can be
significantly lowered, from 1.32J/cm2 damage fluence with 1054/0.5ps only to 1.05 J/cm2 with the simultaneous
presence of 532nm/7ns laser light at a fluence of 8.1 J/cm2. This reduction of LIDT of the sample at 1054nm/0.5ps
continues as the fluence of 532nm/7ns laser light simultaneously present increases. The reduction of LIDT does not
occur when the 2 pulses are temporally separated. This paper will also present dual wavelength LIDT results of
commercial dichroic beam-combining optics simultaneously exposed with laser light at 1054nm/2.5ns and 532nm/7ns.
