Toward the realization of a frequency standard at 1.5 /spl mu/m based on narrow-linewidth erbium lasers and saturated acetylene lines

The work is aimed at the study and development of a high-accuracy frequency standard at 1.5 /spl mu/m, by combining the intrinsic frequency stability of a solid-state laser to the accuracy and reliability of Doppler-free molecular lines. A diode-pumped Er-Yb microlaser is frequency stabilized to the center of /sup 13/C/sub 2/H/sub 2/ saturated absorption lines by means of the frequency modulation technique. A resonant Fabry-Perot cavity containing acetylene at low pressure is used to enhance the field intensity in order to saturate the 1.5 /spl mu/m overtone transitions of the molecule. Two stabilization loops are used to lock the Fabry-Perot cavity to the laser frequency and this last to the peak of the saturation dip. Preliminary experimental results on the Er-Yb laser frequency noise are reported.