Opt Lett. 2018 Sep 15;43(18):4354-4357. doi: 10.1364/OL.43.004354.
We experimentally observe a vortex six-wave mixing (SWM), namely, enhanced four-wave mixing (FWM), signal with its orbital angular momentum transferred from a vortex probe via a photonic band gap (PBG) structure in a hot rubidium vapor cell. By analyzing spatial images and interference patterns, on the one hand, we demonstrate spatial shift and splitting of the images as well as shift of phase singularity for the probe transmission signal under the nonlinear phase of different dressing fields; on the other hand, we observe defocusing and shift of the images as well as shift of phase singularity for the reflected vortex SWM signal by scanning the frequency detuning of a related field. Moreover, we find the interference patterns of the vortex probe can be switched from parallel shape to spiral shape by changing its incident angle. Also, we further research the spiral interference patterns of the transmitted signal by scanning the probe detuning, observing that the number of forks changes with the detuning. We consider the transmitted signal as a combined beam of the linear probe and nonlinear FWM, which are separated under Kerr effect. It is the separation that causes the fork number to change with probe detuning. Our studies are useful for better understanding and manipulation of optical vortices and have wide applications in quantum communication and information processing.
我们实验观察到了涡旋六波混频（SWM），即通过光子带隙（PBG）结构将涡旋探针的轨道角动量传递到热铷蒸汽室中的增强四波混频（FWM）信号。通过分析空间图像和干涉图案，一方面，我们证明了在不同的修饰场的非线性相位下，探针传输信号的图像会发生空间位移和分裂，相位奇点也会发生位移；另一方面，我们通过扫描相关场的频率失谐，观察到反射涡旋 SWM 信号的图像散焦和位移，以及相位奇点的位移。此外，我们发现通过改变入射角可以将探针的干涉图案从平行形状切换到螺旋形状。此外，我们还通过扫描探针失谐进一步研究了透射信号的螺旋干涉图案，观察到叉数随失谐的变化。我们认为透射信号是线性探针和非线性 FWM 的组合光束，它们在克尔效应下分离。正是这种分离导致叉数随探针失谐而变化。我们的研究有助于更好地理解和操纵光学涡旋，在量子通信和信息处理中有广泛的应用。
