Diversity and manipulability of pump-probe absorption spectra for a degenerate two-level system

We present a theoretical study of pump-probe spectra of a degenerate two-level system subject to a magnetic field, which is driven by three different polarized fields and probed by two different polarized fields. In this system, the optical effects of two-photon resonance, coherent hole burning (CHB), as well as electromagnetically induced absorption (EIA) are involved. Based on the match between the pump and probe fields, four sets of electromagnetically induced transparencies (EITs) and two sets of CHBs are included in the coherent system. The types of Mollow absorption and absorption spectra with four main peaks are obtained, in which the absorption peaks are modified by the dips of EITs and CHBs. In the weak coupled fields, six-peak and eight-peak absorption spectra form for the two cases respectively. However, for the strong coupled fields, the absorption spectra with seven or nine peaks arise due to the dressed levels. With the adjustable coupled detunings, the transparent windows of EIT and CHB can be manipulated according to the need, and with the technique of manipulation of spectra, the enhanced atomic absorption with two subnatural-linewidth peaks can be achieved.