Accurate frequency measurements in the infrared using stabilized CO/sub 2//OsO/sub 4/ lasers

A new calibration of an OsO/sub 4/ absolute frequency grid is reported with an uncertainty less than 100 Hz in the 28/29 THz range (/spl delta/v/v/spl sim/3/spl times/10/sup -17/). A precedent determination has been performed fifteen years before, with uncertainties ranging from 50 Hz to 2 kHz. These OsO/sub 4/ transitions confer high metrological performances to CO/sub 2/ lasers when frequency locked on the third harmonic of the saturated resonances. We report also recent results on the stability of the BNM-LPTF CO/sub 2//OsO/sub 4/ optical frequency standard in terms of short-term stability of 3/spl times/10/sup -14//spl tau//sup - 1/2 / and long term stability of 2.4/spl times/10/sup -15/ for 3000 s of integration time. This result corresponds, to our knowledge, to the best stability achieved, up to now, in the optical domain.