关键词: 抽运-探测/
自旋定向/
电荷分离/
超快动力学
English Abstract
Pump-orientation-probe technique and its applications
Chen Cong1,Liang Pan1,
Hu Rong-Rong1,
Jia Tian-Qing1,
Sun Zhen-Rong1,
Feng Dong-Hai1,2
1.State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China;
2.Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Fund Project:Project supported by the National High Technology Research and Development Program of China (Grant No. 2014AA123401), the National Key Research and Development Program of China (Grant No. 2016YFB0501601), the National Natural Science Foundation of China (Grant Nos. 11374099, 11474097, 11727810, 61720106009, 11474096), the Shanghai Municipal Science and Technology Commission, China (Grant No. 16520721200), and the 111 Project, China (Grant No. B12024).Received Date:31 January 2018
Accepted Date:02 March 2018
Published Online:05 May 2018
Abstract:The pump-orientation-probe technique is a recently-developed novel transient measurement technique, which has unique advantages in probing the ultrafast dynamics of charge separation in colloidal nanostructures. In this technique, the linearly-polarized pump pulse is applied to generating electron-hole pairs, and the circularly-polarized spin-orientation pulse is used to establish the electron spin polarization, whose dynamics is detected by monitoring the polarization change of the linearly-polarized probe pulse. Initially, the wavefunctions of the electron-hole pairs are spatially overlapped, and the lifetime of the electron spin is short because of the strong electron-hole exchange interaction. If the electrons or the holes are trapped by the surfaces of the colloidal nanostructures, the spatial separations between the electrons and the holes weaken the exchange effect, and thus the lifetime of the electron spin is largely lengthened. The evolutions of electrons and holes from their spatial overlap to separation can be revealed by monitoring the change of the electron spin dynamics. Based on the introduction of the conventional two-beam carrier pump-probe and spin pump-probe techniques, the features and optical layout of three-beam pump-orientation-probe technique are described in depth. The application to probing negative or positive photocharging in CdS colloidal quantum dots is taken for example and discussed in depth. Compared with the conventional time-resolved absorption or time-resolved fluorescence spectroscopy, the pump-orientation-probe technique can detect the dynamics of trapping electrons or holes and distinguish the type of charging state easily and directly, which has particular advantages under the high-power excitation condition. Further outlook of the three-beam pump-orientation-probe technique is also presented finally.
Keywords: pump-probe/
spin orientation/
charge separation/
ultrafast dynamics
