Published online by Cambridge University Press: 15 December 2001
This paper presents the principle of an air wavelength standardfor high accuracy length metrology. According to the definition ofthe Mètre, nanometric accuracy by interferometric measurementtechniques can be reached only for measurements made under vacuumor by taking into account the fluctuations of the refractive indexof air. We have developed a new type of laser source whosewavelength is insensitive to slow fluctuations of the refractiveindex of air. The sensitivity of our air wavelength standard tosome characteristics (such as temperature, pressure, ageingbehaviour...) has been measured. Results show that the relativeuncertainty level of the wavelength of our source is below 10−8.