Orbital Angular Momentum Spectral Dynamics of GaN Excitons Excited by Optical Vortices
Orbital Angular Momentum Spectral Dynamics of GaN Excitons Excited by Optical Vortices
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DOI：
10.7567/jjap.52.08jl08
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发表时间：
2013-05
影响因子：
1.5
通讯作者：
Kyohhei Shigematsu;Y. Toda;K. Yamane;R. Morita
中科院分区：
文献类型：
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作者：
Kyohhei Shigematsu;Y. Toda;K. Yamane;R. Morita
我们报道了GaN激子光激发轨道角动量（OAM）态的相干动力学。测量是通过使用光涡旋（OV）脉冲的泵浦-探测四波混频（FWM）进行的，其中泵浦OV脉冲将其OAM转移到激子的质量动量中心，并且探测到OAM经由FWM与探测脉冲的转换。特别地，我们使用OAM分辨光谱对信号进行了分析，这使我们能够评估激子在时间和空间中的失相动力学。结果表明，使用具有非零OAM的OV脉冲实现了接近完美的转换，并且其空间相干性在退相时间期间保持高，清楚地表明激子保持由泵浦OV传输的OAM。相反，当入射脉冲之一有意包括无OAM分量时，与不完美转换相关联的分量变得显著。该效应通过具有多个OAM的泵激发的FWM清楚地证实。
We report on the coherent dynamics of the photoexcited orbital angular momentum (OAM) states of GaN excitons. The measurements were performed by a pump-probe four-wave mixing (FWM) using optical vortex (OV) pulses, where the pump OV pulse transfers its OAM to the center of mass momentum of excitons and the conversion of OAM via FWM with the probe pulse is detected. Especially, we performed analysis of the signal using an OAM-resolved spectroscopy, which allows us to evaluate the dephasing dynamics of excitons in time and space. The results indicate that near perfect conversion is achieved using the OV pulses with nonzero OAM and its spatial coherence remains high during the dephasing time, clearly indicating that the excitons keep the OAM transferred by the pump OV. In contrast, the component associated with the imperfect conversion becomes significant when one of the incident pulses intentionally includes an OAM-free component. The effect is clearly confirmed by the FWM excited by the pump with multiple OAM.