Progress toward absolute frequency measurements of the /sup 127/I/sub 2/-stabilized Nd:YAG laser at 563.2 THz/532 nm

Progress on the development of a frequency chain devoted to the absolute frequency measurement of /sup 127/I/sub 2/-stabilized lasers around 563.2 THz/532 nm is reported. The aim of this work is the improvement of the accuracy-by at least one order of magnitude-of the absolute frequency of this standard. The scheme is based on the frequency combination of two well-known optical frequency standards, namely a CO/sub 2/ laser stabilized on OsO/sub 4/, and a 778-nm diode laser stabilized on Rb measured, at BNM-LPTF, against a cesium primary standard with 2/spl times/10/sup -13/ and 2/spl times/10/sup -12/ relative uncertainty respectively. This last value gives the ultimate accuracy of the reported chain.