Saturated dispersion spectroscopy of OsO/sub 4/

An optical double-frequency phase comparator is proposed for detection of sub-Doppler saturated dispersion resonances of the OsO/sub 4/-absorber. This technique exhibits high sensitivity and small dependence of the background on the optical geometry. Experimental comparison of the phase resonances with normal Lamb-dips is presented. It was shown that the gain of sensitivity corresponds to the one for the method of heterodyne amplitude detection. However, the proposed technique provides the value of the signal which is free of photodetector nonlinearity and misalignment.