Ultraprecise measurement of thermal coefficients of expansion.
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 DeltaT causes a change in interferometer length DeltaL, which shifts the resonance frequencies by Deltanu. Then alpha = (1/DeltaT)(DeltaL/L) = (1/DeltaT)(Deltanu/nu). alpha can be measured with precision limited ultimately by the stability of the stabilized laser (1:10(9) with presently available commercial lasers). alpha vs temperature has been measured for samples of Owens-Illinois Cer-Vit, Corning ULE silica, and Schott low expansion glass-ceramic.
Jacobs
S F
SF
Bradford
J N
JN
Berthold Iii
J W
JW