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Absorption measurement of high-reflectance coated mirrors at 193 nm with a Shack–Hartmann wavefront sensor

Absorption measurement of high-reflectance coated mirrors at 193 nm with a Shack–Hartmann... Abstract. All dielectric high-reflectance (HR) mirror coatings consisting of AlF 3 / LaF 3 / oxide layers were deposited on deep-ultraviolet-grade fused silica and CaF 2 . A novel technique was employed to measure the absorption of these mirrors during irradiation by a 193-nm ArF excimer laser source. The method involves the application of a photothermal measurement technique. The setup uses a Shack–Hartmann wavefront sensor to measure wavefront deformation caused by the heating of the coating by the ArF beam. Laser calorimetric measurements of absorption were used to calibrate the wavefront sensor. The new test setup was used to investigate HR mirror coatings both before and after exposure to high average power ArF laser beams. HR mirror samples were irradiated by a 193-nm kilohertz laser source for either 500 million or 18.6 billion pulses. The differences between wavefront distortion measured inside the beam footprint compared to measured outside the beam footprint can be explained by compaction of the coating in the area heated by the ArF laser. Interesting wavefront-distortion results from testing mirrors with either fused silica or CaF 2 substrates can be explained by considering the figure of merit of these materials for excimer-laser mirror substrates. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Optical Engineering SPIE

Absorption measurement of high-reflectance coated mirrors at 193 nm with a Shack–Hartmann wavefront sensor

Optical Engineering , Volume 51 (12) – Dec 1, 2012

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References (22)

Publisher
SPIE
Copyright
© 2012 Society of Photo-Optical Instrumentation Engineers (SPIE)
Subject
Special Section Papers
ISSN
0091-3286
eISSN
1560-2303
DOI
10.1117/1.OE.51.12.121803
Publisher site
See Article on Publisher Site

Abstract

Abstract. All dielectric high-reflectance (HR) mirror coatings consisting of AlF 3 / LaF 3 / oxide layers were deposited on deep-ultraviolet-grade fused silica and CaF 2 . A novel technique was employed to measure the absorption of these mirrors during irradiation by a 193-nm ArF excimer laser source. The method involves the application of a photothermal measurement technique. The setup uses a Shack–Hartmann wavefront sensor to measure wavefront deformation caused by the heating of the coating by the ArF beam. Laser calorimetric measurements of absorption were used to calibrate the wavefront sensor. The new test setup was used to investigate HR mirror coatings both before and after exposure to high average power ArF laser beams. HR mirror samples were irradiated by a 193-nm kilohertz laser source for either 500 million or 18.6 billion pulses. The differences between wavefront distortion measured inside the beam footprint compared to measured outside the beam footprint can be explained by compaction of the coating in the area heated by the ArF laser. Interesting wavefront-distortion results from testing mirrors with either fused silica or CaF 2 substrates can be explained by considering the figure of merit of these materials for excimer-laser mirror substrates.

Journal

Optical EngineeringSPIE

Published: Dec 1, 2012

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