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PL and broadband PLE spectra of the exciton (X) and biexciton (XX). The excitation power is , which corresponds to an excitation intensity of about . The energy structure for level A is shown on the right. Populations of and states relax into each lowest states and via incoherent processes. Coherent effect in and states can be evaluated from X-PL and XX-PL, respectively.
PLE spectra of X and XX for three excitation powers. The structure of the PLE spectra of X change from Lorentzian-shaped to dip-shaped with increasing excitation.
(a) Energy level structure and physical parameters in the calculation. (b) X population for different excitation powers as a function of detuning energy (energy difference between the excitation photon energy and X energy). The numerical parameters are as follows: , , , , , , where is the optical dipole moment for GaAs bulk.
Schematic energy structure for the exciton–biexciton system. The widths of the arrows between the states show the effective coherence reflecting the optical dipole moments and dephasing times. XD and XXD are dressed states composed of the exciton, the biexciton and the optical field.
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