One-color PL and PLE spectra of two pairs of thick barrier CQDs (CQDs A and B), where the PL spectra were obtained under excitation (absorption band of wetting layer). QD1 and QD2 indicate the two QDs in a single CQD. LO indicates the excited state resonant with the longitudinal optical phonon . (b) PL spectra of the CQDs in Fig. 1(a) excited by one-color (middle and bottom) and two-color (top) excitations. and indicate the excitation energies of the two laser sources, as indicated in Fig. 1(a).
(a) Excitation power dependence of integral PL intensities in CQD A. QD1 and QD2 were excited at and , respectively. With two-color excitation, the detection of QD1 was performed under various intensities with constant excitation, and vice versa. The solid lines are curves fitting the exponent to the excitation power. (b) Diagram of excitation condition and carrier occupation in a thick barrier CQD.
(a) Energy level diagram of QD1. (b) Increment ratio of QD1 PL intensity in CQD A under two-color excitation as a function of excitation intensity , where the intensity was constant (1.0 or ). The solid lines are fitting curves with our model.
(a) Experimental configuration for the time correlated single photon counting measurement pursuant to the Hanbury-Brown-Twiss setup. [(b) and (c)] Second-order autophoton correlation spectra of QD1 (b) and QD2 (c) with one-color excitation. The excitation energy was for QD1 and for QD2 as indicated in Fig. 1(a).
Second-order autophoton correlation spectra of QD2 with one-color excitation. The excitation energy was higher (a) or lower (b) than the LO-phonon resonant level [ and are indicated in Fig. 1(a)]. indicates the decay time of the bunching feature.
Second-order photon correlation spectra with two-color excitation. [(a) and (b)] Autophoton correlation spectra of QD1 (a) and QD2 (b). (c) Cross photon correlation spectrum between QD1 and QD2. indicates the recovery time of the antibunching feature.
Photon detection process in the auto photon correlation measurement.
Carrier occupation diagram in a thick barrier CQD and the photon detection process in the cross photon correlation measurement . The carrier occupation diagram includes the intraband energy relaxation process in each QD.
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