Full aperture laser conditioning of multilayer mirrors and polarizers
Conference
·
OSTI ID:105672
The Inertial Confinement Fusion (ICF) program at LLNL is beginning the design of a 1.8 Megajoule, 0.35-{mu}m, laser system called the National Ignition Facility (NIF). In order to reduce cost, and increase performance, high damage threshold optics are essential. As a result of damage initiating defects, only a small percentage of current as-deposited optical coatings can meet the required damage threshold specification. Work has been conducted in the area of understanding the causes of these nodular defects and how they are related to laser damage. While it is not yet possible to produce defect-free coatings, it has been found that the damage threshold of some coatings can be increased by as much as 2 or more times as a result of pre-illumination at incrementally increasing fluences. This process, termed laser conditioning, has been associated with the ejection of the damage-initiating defects. With current damage thresholds, mirrors and polarizers for the NIF will have to be laser conditioned in order to meet the laser requirements for fluence propagation. LLNL has constructed a system dedicated to laser conditioning of meter-sized HfO{sub 2}/SiO{sub 2} multilayer polarizers and mirrors. The optic is moved in a raster pattern through a stationary 10-Hz rep-rated, 1.064 {mu}m beam with 10-ns pulses. A scatter measurement diagnostic allows on-the-fly evaluation of laser-induced damage during a scan. This system has been used to laser condition optics as large as 73 cm {times} 37 cm. Such optics are now being used on the Beamlet laser system at LLNL. A description of the conditioning process, its effect on the optic, and an analysis of its application to large areas is presented.
- Research Organization:
- Lawrence Livermore National Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 105672
- Report Number(s):
- UCRL-JC--120203; CONF-9505264--6; ON: DE95016628
- Country of Publication:
- United States
- Language:
- English
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