The relative intensities of the Doppler-free signals in the transition from polarized and dispersive signals to absorptive signals of the Na D1 line are calculated theoretically from the approximation of a single cycle of opticalpumping in a four-level system. The transition from polarized signals to saturated signals is made by varying the angle of an analyzer. Since the signal in polarization spectroscopy is mixed with the signal in saturation spectroscopy during the transition, spurious signals due to saturation and polarization effects should be taken into account in the signal analysis of polarization and saturation spectroscopies, respectively. Both theories, of polarization spectroscopy and saturation spectroscopy are unified and applied to the Doppler-free signals of the Na D1 line. The results obtained from the four-level optical pumping theory which mixes polarization spectroscopy with saturation spectroscopy are in good agreement with experimental reports.
A theoretical analysis of the relative intensities of the Doppler-free signals in saturation spectroscopy, velocity selective optical pumping (VSOP) spectroscopy, polarization spectroscopy and a mixing of saturation and polarization spectroscopies is presented using the approximation of a single cycle of optical pumping in a four-level system. An optical pumping process in the Zeeman sublevels is taken into account owing to the important role of spontaneous emission even if the sublevels are degenerate. Arbitrary polarization combinations are considered for pump and probe beams. The similarities and differences between three kinds of spectroscopy are made clear. Both circular and linear optical anisotropies induced by the pump beam are considered in this theoretical calculation. The magnitude and sign of Doppler-free resonances in each spectroscopy are quite different owing to the polarizations of the pump and probe beams. The four-level system is important as a three-level approximation. The results obtained from the four-level optical pumping theory are in good agreement with experimental reports.