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(a) Typical PL spectra of S850 for quasi-resonant excitation where the horizontal axis gives the difference of the excitation energy and the measured PL energy. The black, red, green, and blue lines correspond to 1.363 eV, 1.367 eV, 1.387 eV, and 1.398 eV excitation energies, respectively. (b) The QD band diagram showing the FEL (THz) excitation in red, the PL recombination in blue and the relaxation paths in black arrows. As shown, the QD "A" loses carriers while QD "B" gains carries due to carrier redistribution after THz excitation. The NIR excitation is not shown.
Streak camera image of the PL transient at 8 K from the QD sample S900 for quasi-resonant excitation by the Ti:sapphire laser (a) without FEL pulse and (b) with FEL pulse (quenching by the FEL pulse is indicated by the arrow) of fluence 1 . PL transient integrated over few meV around (c) 1.42 eV (red lines) and (d) 1.40 eV (blue lines) showing the quenching of the PL. The reference transients are shown by dashed lines.
Plot of the measured time resolved PL emission (gray filled region) from QD sample S900 at the (a) high and (b) low energy PL peaks for quasi resonant Ti:sapphire excitation. Quenching of the PL by the FEL pulse occur around 300 ps. The transients are fitted using rate equation model with (solid line) and without (dashed line) interdot carrier transfer channels.
The amount of (a) PL dip depth q and (b) interdot carrier transfer as obtained from the rate equation model fit. The circles and the squares represent samples S900 and S850, respectively. The open (solid) symbols correspond to the higher (lower) energy PL peak.
Sample details at 10 K (Ref. 10).
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