194 369 569.4(5) MHz optical frequency standard based on (C2H2)-C-13 P(16) saturated line

A novel, compact, and reliable Er-Yb:glass laser operating at around 1.54 mum wavelength was developed, with single-frequency and linearly-polarized output power in excess of 10 mW over a continuous tunability range of 17 nm. An external Fabry-Perot resonator containing a low-pressure acetylene cell was used to perform saturation spectroscopy of different absorptions in the (nu(1)+nu(3)) rotovibrational band. By using two nested control loops, the laser was frequency locked to the 1 MHz Doppler-free P(16) line of (C2H2)-C-13 at 1.543 mum wavelength. This particular transition of the acetylene molecule was very recently recommended by the CCL (Comite Consultatif de la Longueur) of the CIPM for the mise en pratique du metre. The frequency stability achieved, as evaluated from the loop error signal, was in the range of +/-40 kHz peak-to-peak (Deltanu/nucongruent toX10(-10)) and the correspondingly calculated Allan deviation is sigma(y)(tau)<10(-11) for integration times taugreater than or equal to1 s and remains significantly low, 10(-11)<sigma(y)(tau)<3X10(-10) for 10(-2) sless than or equal totauless than or equal to50 s and sigma(y)(tau)<10(-12) for tau>70 s. This is the first Italian optical frequency standard in the 1.5 mum band, namely at a frequency of 194 369 569.4(5) MHz and it is now ready for international intercomparisons.