Effects of resonant coupling on terahertz-range coherent phenomena in semiconductor superlattices

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Effects of resonant wave-function coupling on dynamical properties of coherent oscillations, excitonic quantum beat and Bloch oscillation, in semiconductor quantum-well structures have been studied with the use of a femtosecond pump-probe technique. The resonant couplings, which cause anticrossing behaviors of relevant transition energies, were clearly detected by electroreflectance spectroscopy as a function of electric field strength. It is found that the frequency and intensity of the coherent oscillation change significantly under the resonant coupling conditions. The experimental results are reasonably explained by the electric-field-strength dependence of the energies and transition probabilities of the optical transitions observed from the electroreflectance spectra.