基于二维电介质超表面的柱矢量光束偏振阶数调控

Polarization Order Adjustment of Cylindrical Vector Beams by Using Two-Dimensional Dielectric Metasurfaces

超表面在柱矢量光束(CVB)产生方面具有效率高、器件精巧等优势,被广泛用于CVB产生及相关应用,但是该方法存在一个比较大的缺点:超表面的结构是固定的,因此生成的CVB的阶数是不可调的。为了解决该问题,在1550 nm波段实验证明了一种通过模式的加减操作来高效调控CVB偏振阶数的方法。通过将两块超表面级联在一起,实现了CVB偏振阶数的减法运算;在两块超表面之间插入一块半波片,通过反转CVB偏振阶数,实现了CVB偏振阶数的加法运算。最终实现了在-8~8范围内以2为步长的CVB偏振阶数调控操作,实验结果与Jones矩阵的计算结果完全吻合。

Metasurfaces have been widely used to generate cylindrical vector beams（ CVB） owing to its inherent advantages of high efficiency and compact structure. However,a disadvantage of this method is that the polarization order of the generated CVB is hard to be changed,because the structure of metasurface is fixed. To solve this problem,we experimentally demonstrate a simple and efficient method to manipulate the polarization order of CVB through modes addition and subtraction operation at the working wavelength of 1550 nm. By two cascaded metasurfaces,the subtraction operation of polarization orders is realized. Further,a half wave-plate inserted between two metasurfaces is used to reverse polarization orders,in order that the add computation of polarization orders is realized. Experimental results are in goodagreement with the calculation results through Jones matrix,and the polarization order of CVB can be adjusted from-8 to8 with step length of 2 by modes addition and subtraction.