Coherent dynamics of exciton orbital angular momentum transferred by optical vortex pulses
Coherent dynamics of exciton orbital angular momentum transferred by optical vortex pulses
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DOI：
10.1103/physrevb.93.045205
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发表时间：
2016-01-15
影响因子：
3.7
通讯作者：
Toda, Y.
中科院分区：
文献类型：
--
作者：
Shigematsu, K.;Yamane, K.;Toda, Y.
利用简并四波混频（FWM）光谱研究了GaN中激子质心运动的相干动力学。我们从OAM度来评估激子轨道角动量（OAM）动力学，这是由FWM信号的OAM（拓扑电荷）分布得出的。当激子被两个单模LG脉冲激发时，激子OAM的衰减时间明显超过激子退相时间，这可以归因于我们的体样品中激子退相的高度均匀性，因为激子OAM的退相干是由激子退相的角度变化决定的。我们还使用多模LG泵浦脉冲分析了OAM衰变的拓扑电荷(l)依赖关系，这使我们能够同时观察在相同激励条件下不同l值的激子OAM的动力学。l = 1分量的OAM衰减时间通常比l = 0分量的OAM衰减时间长。考虑了激子消相的局部非均匀性的现象学模型支持了与l相关的OAM衰变。
The coherent dynamics of the exciton center-of-mass motion in bulk GaN are studied using degenerate four-wave-mixing (FWM) spectroscopy with Laguerre-Gaussian (LG) mode pulses. We evaluate the exciton orbital angular momentum (OAM) dynamics from the degree of OAM, which is derived from the distributions of OAM (topological charge) of the FWM signals. When excitons are excited with two single-mode LG pulses, the exciton OAM decay time significantly exceeds the exciton dephasing time, which can be attributed to high uniformity of the exciton dephasing in our bulk sample because the decoherence of the exciton OAM is governed by the angular variation in the exciton dephasing. We also analyze the topological charge (l) dependence of the OAM decay using a multiple-mode LG pump pulse, which allows us to simultaneously observe the dynamics of the exciton OAM for different l values under the same excitation conditions. The OAM decay times of the l = 1 component are usually longer than those of the l = 0 component. The l-dependent OAM decay is supported by a phenomenological model which takes into account the local nonuniformity of the exciton dephasing.