Laser-controlled exciton Fano resonance in semiconductor superlattices

Quantum control of excitonic Floquet states in semiconductor superlattices driven by an intense monochromatic laser is examined from a theoretical point of view. High-resolution optical absorption spectra, calculated using multichannel scattering theory with the R-matrix propagation method, clarified that the excitonic Fano resonance structure is induced by the laser field. Each of the physical quantities related to this resonance-such as the spectral intensity, an asymmetry parameter (q-parameter), a resonance width, and so on-shows a characteristic extremum as a function of laser strength (F(ac)) in the vicinity of a critical value of F(ac) where dynamic localization is realized. It has also been shown that this F(ac)-dependence is caused by an ac-Zener coupling between two photon sidebands. Further, we have shown that these quantities are also controlled by changing the laser frequency (ω), as well as F(ac), and the underlying physics is explained on the basis of anticrossing behavior of the two photon sidebands.