The Formula: see text line of Formula: see textRb exhibits non-cycling transitions; therefore, only weak modulation transfer spectroscopy (MTS) signals could be obtained. In this study, however, strong MTS spectra were obtained for the Formula: see text line via optical pumping (OP) of the Formula: see text line of Formula: see textRb. Four linear parallel (lin ∥ lin) and linear perpendicular (lin⊥lin), Formula: see text, and Formula: see text polarization configurations were investigated using an OP laser with four different polarizations such as linear horizontal (P), linear vertical (S), Formula: see text, and Formula: see text polarizations. Under the linear perpendicular configuration, the MTS signal for the Formula: see text transition of the Formula: see text line exhibited approximately a 41-fold increase in the signal slope in the presence of a linearly-polarized OP beam, compared with the signal slope obtained without OP. The calculated MTS spectra for the Formula: see text configuration in the presence of Formula: see text- or Formula: see text-polarized OP beam as an example matched well with experimental observations.
Khan et al. (Wed,) studied this question.