CO/sub 2//OsO/sub 4/ lasers as frequency standards in the 29 THz range

The CO/sub 2/ lasers, frequency stabilized on OsO/sub 4/ transitions around 29 THz, are successfully used as secondary references for visible frequency synthesis and also for high-accuracy spectroscopy in the infrared domain. The BNM-LPTF CO/sub 2//OsO/sub 4/ frequency standards exhibit high metrological performances: a long term reproducibility of /spl plusmn/10 Hz (1/spl sigma/=2/spl times/10/sup -13/) and a stability /spl sigma//sub y/=6.6/spl times/10/sup -14///spl radic//spl tau/ with a Flicker plateau of 4/spl times/10/sup -15/ (/spl Delta//spl nu///spl nu/=0.1) for 300 s to 10/sup 3/ s averaging times. These results and a preliminary study of the main effects which can induce frequency shifts are reported.