Abstract

A novel method for determining thermal expansion coefficients has been devised. It is based on the dependence of Fabry-Perot resonances on the mirror separation. The expansion sample is formed into an etalon spacer, with highly reflecting endplates optically contacted to each end. The Fabry-Perot resonances are probed by variable radiofrequency sidebands derived from a frequency stabilized 633-nm He–Ne laser. A change in sample temperature ΔT causes a change in interferometer length ΔL, which shifts the resonance frequencies by Δν. Then α = (1/ΔT)(ΔL/L) = (1/ΔT)(Δ/ν). α can be measured with precision limited ultimately by the stability of the stabilized laser (1:10⁹ with presently available commercial lasers). α vs temperature has been measured for samples of Owens-Illinois Cer-Vit, Corning ULE silica, and Schott low expansion glass-ceramic.

© 1970 Optical Society of America

Ultraprecise thermal expansion measurements of seven low expansion materials

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