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Proceedings Paper

High-precision thermal expansion measurements using small Fabry-Perot etalons
Author(s): Mark J. Davis; Joseph S. Hayden; Daniel L. Farber
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Paper Abstract

Coefficient of thermal expansion (CTE) measurements using small Fabry-Perot etalons were conducted on high and low thermal expansion materials differing in CTE by a factor of nearly 400. The smallest detectable change in length was ~10-12 m. The sample consisted of a mm-sized Fabry-Perot etalon equipped with spherical mirrors; the material-under-test served as the 2.5 mm-thick spacer between the mirrors. A heterodyne optical setup was used with one laser locked to an ~780 nm hyperfine line of Rb gas and the other locked to a resonance of the sample etalon; changes in the beat frequency between the two lasers as a function of temperature directly provided a CTE value. The measurement system was tested using the high-CTE SCHOTT optical glass N-KF9 (CTE = 9.5 ppm/K at 23 °C). Measurements conducted under reproducibility conditions using five identically-prepared N-KF9 etalons demonstrate a precision of 0.1 ppm/K; absolute values (accuracy) are within 2-sigma errors with those made using mechanical dilatometers with 100-mm long sample rods. Etalon-based CTE measurements were also made on a high-CTE (~10.5 ppm/K), proprietary glass-ceramic used for high peak-pressure electrical feedthroughs and revealed statistically significant differences among parts made under what were assumed to be identical conditions. Finally, CTE measurements were made on etalons constructed from SCHOTT's ultra-low CTE Zerodur(R) glass-ceramic (CTE about -20 ppb/K at 50 °C for the material tested herein).

Paper Details

Date Published: 12 September 2007
PDF: 12 pages
Proc. SPIE 6673, Time and Frequency Metrology, 66730R (12 September 2007); doi: 10.1117/12.734423
Show Author Affiliations
Mark J. Davis, SCHOTT North America, Inc. (United States)
Joseph S. Hayden, SCHOTT North America, Inc. (United States)
Daniel L. Farber, Lawrence Livermore National Lab. (United States)

Published in SPIE Proceedings Vol. 6673:
Time and Frequency Metrology
R. Jason Jones, Editor(s)

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