Doubly resonant terahertz sideband generation in quantum wells: Optical signatures of terahertz-dressed subbands

The propagation of light through quantum wells in the vicinity of a pair of excitonic resonances dressed by a far-infrared (THz) electric field is con sidered. The THz frequency is tuned near resonance with (half) the splittin g between the exciton levels (for an inversion symmetric system). It is fou nd that even if excitation from the crystal ground state to one of the pair of levels is optically forbidden, it may nevertheless have a strong influe nce on the optical spectra due to the THz-induced hybridization of the leve ls (Autler-Townes splitting). If the optical transition from the crystal gr ound state to each of the two levels is allowed, the optical spectra of the pair of dressed levels exhibit multiple peaks.