Ultraprecise Measurement of Thermal Coefficients of Expansion

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 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.

Dimensional stability of fused silica, Invar, and several ultralow thermal expansion materials

“…The method of measurement is an outgrowth of a technique previously described for ultraprecise measurement of thermal expansion coefficients. 7 As shown in Fig. 4, a frequency stabilized laser beam is passed through a Fabry-Perot resonator (FP), which consists of the sample as spacer illumination.…”

P4 - Interferometric Heat-Load Sensing of High Power Solid Laser Medium

“…Multiple internal reflections of the analysis beam occur at the laser crystal's highly parallel end faces. The interference pattern of the transmitted radiation changes with the cavity temperature [3]. The pattern is recorded with a CCD beam camera.…”

Thermal stabilization for accurate dimensional measurement using gallium

“…(1) and (2), the so-called frequency-to-temperature sensitivity of the Fabry-Perot cavity is obtained in the simple form of Eq. (3) as derived by Jacob et al [12]:…”