  The off-resonant AC Stark shift for coherent population trapping (CPT)
resonances probed with Ramsey spectroscopy is investigated experimentally and
theoretically. Measurements with laser-cooled $^{87}$Rb atoms show excellent
quantitative agreement with a simple theory. The shift depends on the relative
intensity of the two CPT light fields, but depends only weakly on the total
intensity. Since the origin of the shift is through couplings of the
interrogation light to off-resonant excited state hyperfine levels, the size
and sign of the shift depend on the specific interrogation scheme. However, the
simple theory shows that for several commonly used interrogation schemes the
off-resonant shift goes to zero at specific values of this relative intensity.
