title: Creating optical near-field orbital angular momentum in a gold metasurface.
abstract: Nanocavities inscribed in a gold thin film are optimized and designed to form a metasurface. We demonstrate both numerically and experimentally the creation of surface plasmon (SP) vortex carrying orbital angular momentum in the metasurface under linearly polarized optical excitation that carries no optical angular momentum. Moreover, depending on the orientation of the exciting linearly polarized light, we show that the metasurface is capable of providing dynamic switching between SP vortex formation or SP subwavelength focusing. The resulting SP intensities are experimentally measured using a near-field scanning optical microscope and are found in excellent quantitative agreements as compared to the numerical results.
authors: †Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors: Ching-Fu
authors: CF
authors: Chen
authors: †Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors: Chen-Ta
authors: CT
authors: Ku
authors: ‡Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan.
authors: Yi-Hsin
authors: YH
authors: Tai
authors: ‡Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan.
authors: Pei-Kuen
authors: PK
authors: Wei
authors: §Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors: Heh-Nan
authors: HN
authors: Lin
authors: †Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors: Chen-Bin
authors: CB
authors: Huang
keywords: Orbital angular momentum; metasurface; optical vortex; plasmonics