194 369 569.4(5) MHz optical frequency standard based on /sup 13/C/sub 2/H/sub 2/ p(16) saturated line

Abstract

A novel, compact, and reliable Er-Yb:glass laser operating at around 1.54 /spl mu/m 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 (v/sub 1/+v/sub 3/) rotovibrational band. By using two nested control loops, the laser was frequency locked to the 1 MHz Doppler-free P(16) line of /sup 13/C/sub 2/H/sub 2/ at 1. 543 /spl mu/m 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, way in the range of /spl plusmn/40 kHz peak-to-peak (/spl Delta/v/v/spl cong/2/spl times/10/sup -10/) and the correspondingly calculated Allan deviation is /spl sigma//sub y/(/spl tau/)<10/sup -11/for integration times /spl tau//spl ges/1 s and remains significantly low, 10/sup -11/70 s. This is the first Italian optical frequency standard in the 1.5 /spl mu/m band, namely at a frequency of 194 369 569.4(5) MHz and it is now ready for international intercomparisons.