Comparison Of Wavelengths To The Primary Standard At The French National Institute Of Metrology

AbstractWe describe some properties of the two beam interferometer that we have built at the "Institut Nationalde Metrologie" for wavelength comparison. We describe particularly the phase shifts between visible wave-lengths at zero path difference.IntroductionThe National Institute of Metrology of the National Conservatory of Arts and Trades is the primary lab-oratory of the National Bureau of Metrology for lengths. It is thus responsible at the national level forthe comparison of measurements of length to the primary standard, that is, to the wavelength of the orangeradiation of krypton 86. To this end we built a two-wave interferometer of the Michelson type, workingin a secondary vacuum to eliminate any index correction. The separating plates are in Brewsterian incidenceto avoid any parasitical interference capable of dephasing the fringes. a a A Fig. 1. General view of the interferometer in its airtight case. The light beams enter and leave by theports at right. At left is the oil diffusion pump and its vacuum reservoir; the primary pump is under the