14 February 2008 Characterization of absorptance losses in optical materials using a high resolution Hartmann-Shack wavefront sensor
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Proceedings Volume 6879, Photon Processing in Microelectronics and Photonics VII; 68791S (2008); doi: 10.1117/12.762579
Event: Lasers and Applications in Science and Engineering, 2008, San Jose, California, United States
Abstract
Lens heating due to absorbed UV laser radiation can diminish the achievable spatial resolution of the lithographic process in semiconductor wafer steppers. At the Laser- Laboratorium Göttingen a measurement system for quantitative registration of this thermal lens effect was developed. It is based upon a strongly improved Hartmann-Shack wavefront sensor with extreme sensitivity, accomplishing precise online monitoring of wavefront deformations of a collimated test laser beam transmitted through the laser-irradiated site of a sample. Caused by the temperature-dependent refractive index as well as thermal expansion, the formerly plane wavefront of the test laser is distorted to form a rotationally symmetric valley, being equivalent to a convex lens. The observed wavefront distortion is a quantitative measure of the absorption losses in the sample. Thermal theory affords absolute calibration of absorption coefficients.
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A. Bayer, F. Barkusky, U. Leinhos, T. Miege, B. Schäfer, K. Mann, "Characterization of absorptance losses in optical materials using a high resolution Hartmann-Shack wavefront sensor", Proc. SPIE 6879, Photon Processing in Microelectronics and Photonics VII, 68791S (14 February 2008); doi: 10.1117/12.762579; https://doi.org/10.1117/12.762579
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KEYWORDS
Absorption

Wavefronts

Quartz

Thermal effects

Wavefront distortions

Wavefront sensors

Deep ultraviolet

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