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Picometer Metrology for Precise Measurement of Refractive Index, Pressure, and Temperature

Published

Author(s)

Jack A. Stone Jr., Patrick F. Egan, Donavon Gerty, Jay H. Hendricks, Douglas A. Olson, Jacob E. Ricker, Gregory E. Scace, Gregory F. Strouse

Abstract

Fabry-Perot interferometers can be used for very precise measurement of the refractive index of gasses. This can enable increased accuracy of interferometer-based length measurement. In addition, because the refractive index of a gas depends on its pressure and temperature, measurements of refractive index can be used to monitor either one of these quantities if the second is known. Recently we have embarked on a project with a goal of measuring pressure with a relative standard uncertainty below 1.4x10^-6. Dimensional metrology with picometer uncertainties is the core of this technique and is the subject of this paper. Refractive index will be measured by comparing two precisely equal displacements (150 mm), where one displacement is in vacuum and the second is in helium and will appear to be slightly longer due to the refractive index. The two displacements must be compared with
Citation
NCSL International Measure
Volume
8
Issue
4

Keywords

dimensional metrology, pressure metrology, interferometry, Fabry-Perot
Created December 18, 2013, Updated February 17, 2017