Zhao Kun, Zhang Zhiyu, Zang Haofeng, Du Jing, Lu Yonghua, Wang Pei
Opt Lett. 2021 Apr 15;46(8):1896-1899. doi: 10.1364/OL.422351.
A pure longitudinal magnetization focal spot is greatly desired by all-optical magnetic recording. In this Letter, a triplex metalens is proposed and demonstrated to possess triple functions of an azimuthal polarization converter, a helical phase plate, and a focusing lens. The three-in-one combination enables conversion of linearly polarized incident light to the first-order azimuthally polarized vortex beam and focusing into a diffraction-limited spot. The state of polarization of the focal spot is measured to be pure circular polarization implying that a pure longitudinal magnetization field can be induced by the inverse Faraday effect. The lateral full width at half-maximum of the focal spot is 1.9 µm, and the experimental conversion efficiency of the metasurface is about 19.3%.
全光磁记录非常需要一个纯纵向磁化焦点光斑。在本信函中，提出并展示了一种三元超透镜，它具有方位角偏振转换器、螺旋相位板和聚焦透镜的三重功能。这种三合一组合能够将线偏振入射光转换为一阶方位角偏振涡旋光束，并聚焦成一个衍射极限光斑。测量得出焦点光斑的偏振态为纯圆偏振，这意味着可以通过逆法拉第效应感应出纯纵向磁化场。焦点光斑的横向半高全宽为1.9 µm，超表面的实验转换效率约为19.3%。
