Superfluorescent pulsed emission from biexcitons in an ensemble of semiconductor quantum dots
Superfluorescent pulsed emission from biexcitons in an ensemble of semiconductor quantum dots
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DOI：
10.1088/0953-8984/21/19/195802
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发表时间：
2009-05-13
影响因子：
2.7
通讯作者：
Itoh, T.
中科院分区：
文献类型：
--
作者：
Miyajima, K.;Kagotani, Y.;Itoh, T.
使用光学克尔门方法测量了嵌入 NaCl 基质中的 CuCl 量子点 (QD) 中双激子的皮秒时间分辨光致发光。仅在双激子共振双光子激发下，首次观察到双激子态的超快脉冲发射。这意味着为了触发脉冲发射，双激子和激子态之间的完全粒子数反转是必要的。此外，脉冲发射的时间曲线对激发强度的依赖性的本质表明，峰值强度与激发的量子点数量的平方成正比。我们得出的结论是，这种现象是由超荧光引起的，即由共振电磁波耦合的许多孤立激发态的协同自发辐射衰变。在本研究中，首次在半导体量子点集合中观察到这种现象。本文提出的结果表明，控制量子点系综中电子激发态的微观相干动力学是可能的。
Picosecond time-resolved photoluminescence from biexcitons in CuCl quantum dots (QDs) embedded in a NaCl matrix has been measured using an optical Kerr gate method. Ultrafast pulsed emission from the biexciton states was observed for the first time, only under resonant two-photon excitation of biexcitons. This implies that complete population inversion between the biexciton and exciton states is necessary in order to trigger the pulsed emission. In addition, the nature of the dependence of the time profiles of the pulsed emission on the excitation intensity reveals that the peak intensity is directly proportional to the square of the number of excited QDs. We conclude that this phenomenon is caused by superfluorescence, that is, the cooperative spontaneous radiative decay of many isolated excited states coupled by a resonant electromagnetic wave. Such a phenomenon has been observed for the first time in an ensemble of semiconductor QDs in this study. The results presented in this paper show that it is possible to control the microscopic coherent dynamics of electronic excited states in a QD ensemble.