SPECTRAL PURITY AND LONG-TERM STABILITY OF CO2-LASERS AT THE HERTZ LEVEL

Ultra-high-resolution spectroscopy and metrology require very stable l asers with a high-spectral purity, For spectroscopy with a resolution in the range 10-100 Hz at 30 THz, we are developing a new stabilizatio n scheme which acts separately on the long and short term stabilities, We present the results achieved with the first part of our new scheme , which is based upon the stabilization on a saturation signal detecte d in transmission of an active Fabry-Perot cavity. With a laser linewi dth of 3.4 Hz (FWHM) and a Flicker plateau of 0.7 Hz (Delta upsilon/up silon = 2,10(-14)) obtained using a strong OsO4 line as reference, thi s stabilization system already improves the both short and long-term s tabilities obtained by our previous setup which involved an external c ell instead of a Fabry-Perot cavity, We present also the results using a CO2 laser line as frequency reference.