Absolute frequency stabilization of an extended-cavity diode laser against Doppler-free H217O absorption lines at 1.384 μm

We report the frequency stabilization of a cw extended-cavity diode laser against saturated absorption lines of the H217O isotopologue of water vapor at around 1.384 μm. The saturation of rotovibrational transitions is achieved by filling a high-finesse optical resonator with H2 O at low pressure and by locking the laser frequency to the resonator by using the Pound-Drever-Hall technique. Absolute frequency stabilization is obtained, locking the cavity resonance to the center of the sub-Doppler line by means of the wavelength modulation method. A relative frequency stability of σy (τ)= 10-18(0. 1τ-2 + 0.9)1/2 is demonstrated for integration times in the range 4 ms< τ<30 S. © 2009 Optical Society of America