Fabry-Perot displacement interferometry in air

In earlier work, we have demonstrated the use of Fabry-Perot interferometry to measure displacements of up to 50 mm with a fractional accuracy of 4 x 10-10 in vacuum. The initial work was done at a wavelength of 633 nm, and the more recent work was done at 1560 nm. We now seek to extend the approach to displacement measurements in air. A well-known approach to compensate for the refractive index of air without relying on independent measurements of the temperature and pressure is to use two wavelengths. In this work, we supplement our implementation at 1560 nm with an additional laser at 1064 nm in order to control for the dispersion of air