by Haoran Ren, Xiangping Li, Qiming Zhang, and Min Gu On-chip noninterference angular momentum multiplexing of broadband light by Haoran Ren, Xiangping Li, Qiming Zhang, and Min Gu Science Volume ():aaf1112 April 7, 2016 Published by AAAS

Fig. 1 The principle of on-chip non-interference AM multiplexing of broadband light. The principle of on-chip non-interference AM multiplexing of broadband light. (A) Four selected AM beams of l0 = –4, s = –1 (AM1), l0 = –2, s = –1 (AM2), l0 = +2, s = +1 (AM3) and l0 = +4, s = +1 (AM4) are co-axially overlapped as the AM-superposed beams (l0 and s are the modal indices for OAM and SAM, respectively). (B) The schematic of a NRA multiplexing unit consisting of nano-groove structures and the mode-sorting nano-ring slits. (C) The mechanism for AM mode-sorting by nano-ring slits that have different sizes and lateral shifts. (D) The NAMMC integrated by an array of 8 by 8 NRA units. (E) Concept of on-chip processing of AM-multiplexed images over a broadband by the NAMMC. Haoran Ren et al. Science 2016;science.aaf1112 Published by AAAS

Fig. 2 Distinctive AM mode-sorting selectivity by a size-varying nano-ring slit. Distinctive AM mode-sorting selectivity by a size-varying nano-ring slit. (A) The theoretically calculated effective index differences (red curves) and the MF (black curves) for the plasmonic modes with total AM of L = ±1 (solid lines) and L = ±3 (dashed lines) for nano-ring slit with Rin1 = 75 nm (upper) and Rin2 = 200 nm (lower), respectively. (B and C) The scanning electron microscopy (SEM) images of the fabricated NRAs consisting of concentric nano-grooves and nano-ring slits with the inner radii of Rin1 (see fig. S1B for 45 degree view) and Rin2 (see fig. S1C for 45 degree view), respectively. The insets are the enlarged view of the nano-ring slits with a scale bar of 100 nm. (D) The numerically-calculated (curves) and experimentally-confirmed (triangles) AM mode-sorting selectivity spectra of the AM beams of l0 = –2, s = +1 (L = –1) and l0 = +2, s = +1 (L = +3) for nano-ring slits with the inner radii of Rin1 (upper) and Rin2 (lower), respectively. The red color marks out the bandwidths (defined as the selectivity ≥ 0.1) of AM mode-sorting selectivity by nano-ring slits. Haoran Ren et al. Science 2016;science.aaf1112 Published by AAAS

Fig. 3 Experimental characterization of chip-scale AM multiplexing based on double concentric and spatially-shifted nano-ring slits enclosed by sections of spatially-shifted nano-grooves. Experimental characterization of chip-scale AM multiplexing based on double concentric and spatially-shifted nano-ring slits enclosed by sections of spatially-shifted nano-grooves. (A) The SEM image of the double nano-ring slits (inset) with Rin1 and Rin2 enclosed by the two sections of shifted grooves with ls = +2. (B) The simulated total intensity distributions of the AM beams of AM1 and AM2 in the longitudinal planes of nano-ring slits. (C) The experimental far-field intensity distributions of the AM beams of AM1 and AM2 in the transverse planes. (D) The experimental cross-section plots of the far-field intensity distributions in (C) as labeled by the dashed white lines. (E to H) The counterparts of (A) to (D) but based on the spatially-shifted nano-ring slits with Rin1 and nano-grooves with ls = +2 (left) and ls = –2 (right). Haoran Ren et al. Science 2016;science.aaf1112 Published by AAAS

Fig. 4 Four-state AM multiplexing through a NRA unit and parallel AM- and wavelength-division multiplexing through the large-scale NAMMC. Four-state AM multiplexing through a NRA unit and parallel AM- and wavelength-division multiplexing through the large-scale NAMMC. (A) The SEM image of the single NRA (see fig. S1D for 45 degree view) in the NAMMC and the two concentric double nano-ring slits (inset). (B) The experimental characterization of the four-state AM multiplexing by dynamically switching on the AM-superposed beams. The images are presented in pseudo colors. (C) Measured modal crosstalk of the four AM modes at different wavelengths. (D) The SEM image of the NAMMC. (E) The experimentally-reconstructed AM- and wavelength-coded images retrieved from the four AM modes of AM1, AM2, AM3 and AM4 (Fig. 1A) at the three different wavelengths. Haoran Ren et al. Science 2016;science.aaf1112 Published by AAAS