基于Pancharatnam-Berry相位和动力学相位调控纵向光子自旋霍尔效应

提出了一种基于Pancharatnam-Berry相位和动力学相位操控纵向光子自旋霍尔效应的方法.理论分析表明:当光场通过一个由Pancharatnam-Berry相位透镜和动力学相位透镜构成的透镜组时,透镜组会存在两个自旋相关的焦点.首先,当左旋和右旋圆偏振光通过微结构相位延迟为π的Pancharatnam-Berry相位透镜时,由于Pancharatnam-Berry相位的自旋相关性,两个圆偏振分量会获得符号相反的Pancharatnam-Berry相位而导致其中一个被聚焦而另一个发散.然后,在Pancharatnam-Berry相位透镜后再插入普通透镜引入动力学相位调制,由于动力学相位是自旋无关,使得这一透镜组,可以在合适的条件下使不同自旋态的光子分别聚焦于纵向上不同焦点处.纵向自旋分裂由两透镜焦距及间距共同决定,因此可以通过改变两个透镜的焦距及其间距获得任意的纵向自旋分裂值.最后,搭建了一套实验装置,所得实验结果与理论结果一致.

Manipulating longitudinal photonic spin Hall effect based on dynamic and Pancharatnam-Berry phase

Photonic spin Hall effect is generally described as a spin-dependent splitting. Previous studies have focused on the transverse spin-dependent splitting of light field. In this work, a method of manipulating the longitudinal photonic spin Hall effect which is based on dynamic and Pancharatnam-Berry phase is proposed. The theoretical analysis demonstrates that the lens group consisting of a Pancharatnam-Berry phase lens and a dynamic lens has two spin-dependent foci. Firstly, because Pancharatnam-Berry phase is spin-dependent, the left- and right-handed circularly polarized component can respectively acquire a Pancharatnam-Berry phase with opposite sign when a linearly polarized light beam passes through the Pancharatnam-Berry phase lens with phase retardation \${\text{π}}$\. It leads one circularly polarized component to be focused and the other diverged. This is essentially the spin-dependent splitting of light field in momentum space, which is caused by Pancharatnam-Berry phase. And then, an ordinary lens is inserted behind the Pancharatnam-Berry phase lens to introduce a dynamic phase modulation. Due to dynamic phase being spin-independent, the constructed lens group can focus the photons with different spin states at different focal points longitudinally under the appropriate conditions. In other words, the lens group has two spin-dependent focal points. The two focal points split the photons with different spin states in the longitudinal direction. The longitudinal spin-dependent splitting is dependent on the focal lengths of the two lens and the distance between the two lenses. By changing the three parameters, arbitrary longitudinal spin-dependent splitting can be obtained. Lastly, an experimental system is set up to verify the theoretical results. The relationship between the spin-dependent splitting and the distance between the two lenses is measured. By introducing a Glan laser polarizer and a quarter wave-plate, the circularly polarized chirality of the light field at the focal point is also measured. These experimental results are all in good agreement with the theoretical analyses. These results are helpful in understanding the physical origin of photonic spin Hall effect and developing novel photonic devices based on photonic spin Hall effect.