Progress toward absolute frequency measurements of the 127 I2-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 127I2-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 wellknown optical frequency standards, namely a CO2 laser stabilized on OsO4, and a 778-nm diode laser stabilized on Rb measured, at BNM-LPTF, against a cesium primary standard with 2 10 13 and 2 10 12 relative uncertainty respectively. This last value gives the ultimate accuracy of the reported chain.