Effects of undercoats and overcoats on damage thresholds of 248 nm coatings
Previous experiments have demonstrated that 1064 nm high reflectors benefit from the addition of halfwave silica overcoats, and that 1064 nm antireflection coatings can be improved by adding halfwave silica undercoats or barrier layers. In each case, a statistical improvement of about 50% has been observed. This paper reports similar results for coatings designed for 248 nm. The high reflectors were scandia/magnesium fluoride quaterwave stacks. Three design variations were tested: with no overcoat, with a halfwave silica overcoat, and with a halfwave magnesium fluoride overcoat. The presence of the overcoat more than doubled the threshold of the reflectors. The highest threshold, 8.5 joules/sq. cm, was measured on a reflector with a magnesium fluoride overcoat. Two material combinations were used for the four-layer antireflection coatings: scandia/silica and scandia/magnesium fluoride. Each of these combinations was coated without a barrier layer, with a silica barrier layer, and with a magnesium fluoride barrier layer. The barrier layer was an undercoat with a halfwave optical thickness. Varying degrees of improvement in thresholds, ranging up to 50%, were found in all cases with barrier layers. The highest thresholds exceeded 6 joules/sq. cm for scandia/silica coatings with silica barrier layers.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA); Optical Coating Lab., Inc., Santa Rosa, CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5264607
- Report Number(s):
- UCRL-86711; CONF-811117-3; ON: DE82010060
- Country of Publication:
- United States
- Language:
- English
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ALKALINE EARTH METAL COMPOUNDS
ANTIREFLECTION COATINGS
CHALCOGENIDES
COATINGS
DEPOSITION
ELECTROMAGNETIC RADIATION
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
KRYPTON COMPOUNDS
KRYPTON FLUORIDES
LASER RADIATION
MAGNESIUM COMPOUNDS
MAGNESIUM FLUORIDES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
RADIATIONS
RARE GAS COMPOUNDS
SCANDIUM COMPOUNDS
SCANDIUM OXIDES
SILICON COMPOUNDS
SILICON OXIDES
SURFACE COATING
TRANSITION ELEMENT COMPOUNDS