Compact refractometer applied to measurements of the refractive index of air and its density fluctuations

H. Fang; Patrick Juncar

doi:10.1117/12.357777

17 August 1999 Compact refractometer applied to measurements of the refractive index of air and its density fluctuations

H. Fang, Patrick Juncar

Author Affiliations +

Proceedings Volume 3745, Interferometry '99: Applications; (1999) https://doi.org/10.1117/12.357777
Event: International Conference on Optical Metrology, 1999, Pultusk Castle, Poland

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.

Citation Download Citation

H. Fang and Patrick Juncar "Compact refractometer applied to measurements of the refractive index of air and its density fluctuations", Proc. SPIE 3745, Interferometry '99: Applications, (17 August 1999); https://doi.org/10.1117/12.357777

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