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The optical absorption spectra in a quantum well driven both by an intense terahertz (THz) and by an optical pulse are theoretically investigated within the theory of density matrix. We found that the optical absorption spectra and the splitting of the excitonic peaks splitting can be controlled by changing the THz field intensity and/or frequency. The Autler–Towns splitting is a result of the THz nonlinear dynamics of confined excitons, which is in agreement with the experiments. In addition, the dependence of the optical absorption on the quantum well width and the carrier density is also discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The radiative recombination of triplet exciton, is studied here theoretically in inorganic amorphous and organic crystalline semiconductors. A new time-dependent exciton–spin–orbit–photon interaction operator derived recently is used to calculate rates of radiative recombination of triplet excitons and the corresponding radiative lifetimes. It is illustrated that the new operator gives rise to a first order non-zero term responsible for the triplet photoluminescence. Results agree quite well with the known experimental results. [ABSTRACT FROM AUTHOR]