Gas modulation refractometry (GAMOR) is a methodology that can mitigate the influence off luctuations and drifts in Fabry-Pérot cavity–based refractometry. This paper presents a thorough description of its principles, what it enables, and its applicability. An overview of the latest results is presented, including the realization of a system based upon a cavity spacer made of Invar that allows for detection of N2 with sub-ppm precision, and a characterization procedure that allows for assessment of N2 with an accuracy at low-ppm levels.
This project (QuantumPascal, 18SIB04) hasreceived funding from the EMPIR programme cofinanced by the Participating States and from theEuropean Union's Horizon 2020 research andinnovation programme. The authors acknowledgesupport from the Swedish Research Council (VR)(Project No. 621-2015-04374); the Umeå UniversityIndustrial Doctoral School (IDS); the VinnovaMetrology Programme (Project Nos. 2018-04570 and2019-05029); and the Kempe Foundations (ProjectNo. 1823, U12).