Optical frequency measurement of the H(12)C(14)N Lamb-dip-stabilized 1.5-microm diode laser

We have measured the frequency of the P(27) line of H(12)C(14)N at 1556 nm, using the 778-nm two-photon transition of Rb as a frequency reference. The measured frequency was 192, 622, 446.9 +/- 0.1 MHz. We believe that this experiment is the first absolute frequency measurement of a laser stabilized to a saturation dip at 1.5 microm and also the most accurate measurement of a 1.5-microm optical frequency.