Origin of the spectral coherence in dynamically broadened Rabi sidebands

We demonstrate the coherent nature of dynamic Rabi-shifted sidebands arising when a picosecond probe laser interacts with a weakly ionized laser-generated microplasma. The coherence is manifested as spectral fringes observed in the sideband spectra. A model is presented that quantitatively predicts both the spectral phase and the spectral interference measured in the sidebands.