We study the formation of adiabatic states upon strong laser coupling of two levels with non-degenerate hyperfine (HF) structure. A typical Autler-Townes (AT) type of experiment in the ladder excitation scheme 3S1/2-3P3/2-4D5/2, which is conveniently accessible by visible laser radiation sources, is investigated theoretically. The strong field couples the 3P3/2 and 4D5/2 states, creating the adiabatic (laser-dressed) states, which are then probed by a weak laser field on the 3S1/2 -3P3/2 transition. Both laser fields are linearly polarized, implying the selection rule MF=0 for Zeeman sublevels, which allows us to consider each subset of mutually coupled HF levels with the same MF as an independent multilevel system. The probe laser intensity is chosen weak enough, in order to avoid optical pumping and mixing of the ground state HF components. Doppler broadening due to atomic velocity distribution is not taken into account, which is justified in laser-atom interactions in supersonic atomic beams.
We investigate numerically the population of state 4D5/2 as a function of the probe laser detuning for different values of the coupling field strength and detuning. Our numerical calculations are based on the Optical Bloch Equations (OBEs) formalism for the density matrix equations of motion. The system of OBEs for the diagonal and off-diagonal elements is solved numerically using the Split Operator Technique. Analysis of the non-resonant adiabatic mixing of HF levels by the strong laser field reveals some intuitively unexpected features of the AT spectra. First, the intensities of the bright peaks diminish with the increase of the coupling field strength, such that the peak ratio is inversely proportional to the coupling Rabi frequency squared. Second, and most interesting from applications point of view, it is possible to excite two uncorrelated (orthogonal) configurations of adiabatic states, by using the appropriate choice of probe laser detuning for excitation from F=1 or F=2 HF ground state components. Simultaneous use of two probe fields pulses leads to interesting perspectives to form a two-component bichromatic polariton, where a single strong control laser field can drive the independent propagation of the two uncoupled probe field pulses.

We acknowledge support from the Trilateral grant of the Latvian, Lithuanian, and Taiwanese Research Councils “Quantum and Nonlinear Optics with Rydberg-State Atoms” FP-20174-ZF-N-100.