NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.
Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.
An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Performance of a dual Fabry-Perot cavity refractometer
Published
Author(s)
Patrick F. Egan, Jack A. Stone Jr., Jay H. Hendricks, Jacob E. Ricker, Gregory E. Scace, Gregory F. Strouse
Abstract
We have built and characterized a refractometer that utilizes two Fabry-Perot cavities formed on a dimensionally stable spacer. In the typical mode of operation, one cavity is held at vacuum and the other cavity is filled with nitrogen gas. The differential change in length between the cavities is measured as the difference in frequency between two helium-neon (633 nm) lasers, one locked to the resonance of each cavity. This differential change in optical length is a measure of the gas refractivity. Using the known values for the molar refractivity and virial coefficients of nitrogen, and accounting for cavity length distortions, the device could be used as a high-resolution, multi-decade pressure sensor. We describe the performance of the refractometer and also present the equations needed to calculate pressure from gas refractivity.
Egan, P.
, Stone, J.
, Hendricks, J.
, Ricker, J.
, Scace, G.
and Strouse, G.
(2015),
Performance of a dual Fabry-Perot cavity refractometer, Optics Letters, [online], https://doi.org/10.1364/OL.40.003945
(Accessed October 16, 2025)