We report a simplified all-optical scheme that achieves dynamical switching between electromagnetically induced transparency (EIT) and absorption (EIA) in a Λ-type atomic system using only two lasers. The switch is controlled via the polarization (σ + /σ − ) and propagation direction of the optical fields. By applying a weak magnetic field, we spectroscopically resolve the degenerate transition into Zeeman-split subsystems and identify an effective N-type pathway as the physical origin of the switching. Theoretical analysis based on dressed-state perturbation theory reveals that the EIT–EIA transition results from constructive quantum interference between secondary dressed states. The scheme also generates tunable dual transparency windows, enabling potential applications in multi-channel signal routing and polarization-controlled slow-light devices.
Liu et al. (Fri,) studied this question.