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Proceedings Paper

Compact refractometer applied to measurements of the refractive index of air and its density fluctuations
Author(s): H. Fang; Patrick Juncar
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Paper Abstract

We describe a new compact refractometer for air refractive index measurements. It is based on a double plane-plane Fabry Perot interferometer whose cavities of different thickness are illuminated independently by the same tunable frequency laser diode. A first one millimeter thick cavity allows unambiguous identification of the transmission peak of the second (100 mm); the laser frequency being servo- locked to the latter. This refractometer does not require any part to be evacuated during the measurement procedure. The absolute value of the refractive index of air and its fluctuations are obtained in real time by beat frequency technique combined with an optical frequency reference. Measurements provide a resolution of order 10-10 and a relative accuracy of a few times 10-8. We also describe how this refractometer is used to measure the fluctuations of the density of air used to make buoyancy corrections in mass standard comparisons. Other possible applications of our refractometer, in particular for the determination of the water vapor concentration in air are reviewed.

Paper Details

Date Published: 17 August 1999
PDF: 7 pages
Proc. SPIE 3745, Interferometry '99: Applications, (17 August 1999); doi: 10.1117/12.357777
Show Author Affiliations
H. Fang, Bureau International des Poids et Mesures (France)
Patrick Juncar, Conservatoire National des Arts et Metiers (France)


Published in SPIE Proceedings Vol. 3745:
Interferometry '99: Applications
Werner P. O. Jueptner; Krzysztof Patorski, Editor(s)

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