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Minizing Spatial-Dispersion-Induced Birefringence in Crystals Used for Precision Optics by Using Mixed Crystals of Materials With the Opposite Sign of the Birefringence

Published

Author(s)

John H. Burnett, Zachary H. Levine, Eric L. Shirley

Abstract

We recently measured and calculated an intrinsic birefringence in CaF2 and BaF2 cubic crystals in the ultraviolet (UV). These results present serious problems for use fo these crystalline materials for precision optics in the UV, e.g., for UV optical lithography. Since we found the intrinsic birefringence of CAF2 and BaF2 have opposite sign, we propose a correction solution in which a mixed crystal Ca1-xBaxF2 is made which effectively zeroes out the birefringence of the crystal at a given wavelength, for an appropriately chose x value. The appropriate x value is given approximately by the inverse ratio of the birefringences of CaF2 and BaF2. Our calculations indicate that SrF2 has a birefringence that is also opposite in sign that of CaF2. In this case a mixed crystal Ca1-xSrx SrxF2 could also zero out the birefringence. Optical components such as lenses and beam splitters could be made of these mixed crystals that would be free of intrinsic birefringence aberrations at a chosen wavelength. These could be used as components of precision optical systems at this wavelength, such as photolithography projection systems.
Citation
Minizing Spatial-Dispersion-Induced Birefringence in Crystals Used for Precision Optics by Using Mixed Crystals of Materials With the Opposite Sign of the Birefringence

Keywords

BaF<sub>2</sub>, barium fluoride, birefringence, CaF<sub>2</sub>, calcium fluoride

Citation

Burnett, J. , Levine, Z. and Shirley, E. (2001), Minizing Spatial-Dispersion-Induced Birefringence in Crystals Used for Precision Optics by Using Mixed Crystals of Materials With the Opposite Sign of the Birefringence, Minizing Spatial-Dispersion-Induced Birefringence in Crystals Used for Precision Optics by Using Mixed Crystals of Materials With the Opposite Sign of the Birefringence (Accessed May 22, 2024)

Issues

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Created July 31, 2001, Updated February 17, 2017