Numerical study on uncertainty of two-color method

The two-color method is one of the commonly used approaches for converting a length measured in air to a length in vacuum to eliminate the influence of the refractive index of air. However, the error of the technique is not well known. We investigate this uncertainty based on a generalized expression of the two-color method proposed in this paper and using numerical simulations. Numerical calculations reveal the change of the error with temperature, air pressure, and wavelengths. These characteristics can be used to optimize the two-color method.