Localization of a Three-Level Cascade Atom via Resonant Absorption

We show that it is possible to localize a three-level cascade atom under the
resonance condition when it passes through a standing-wave field. The
localization peaks appear at the nodes of the standing-wave field, the detecting probability is 50% in the subwavelength domain, and the peaks
are narrower on the resonance than the off-resonance. The absorption is
the same as that in the usual two-level medium at the nodes and is greatly suppressed outside the nodes due to the Autler--Townes splitting. This is in sharp contrast to the lambda scheme, in which the localization is impossible under the same resonance condition due to the depletion of population of the initial state by the probe field at the nodes and the electromagnetically induced transparency outside the nodes.