A spectroscopic technique using lasers to locate absorption maxima with great precision. In saturation spectroscopy the laser beam is split into an intense saturating beam and a less intense beam that pass through the cavity containing the sample in almost opposite directions. The saturating beam sometimes excites molecules, which are shifted to its frequency by the Doppler effect. The other beam gives a modulated signal at the detector if it is interacting with the same Doppler-shifted molecules. These molecules are not moving parallel to the beams and have an extremely small Doppler shift, thus providing very high resolution. See also Lamb-dip spectroscopy.