# Plasmonic and Dielectric Metasurfaces: Design, Fabrication and Applications
## 2 Plasmonic Metasurfaces  
Plasmonic metasurfaces are composed of metal nanoparticles based on the plasmon resonances. Several typical types of plasmonic metasurfaces and previous works are displayed in Table 1: (1) metal V-shaped nano-antennas are designed and fabricated on silicon substrate using the electron-beam lithography method to manipulate the phase of scattering light and to generate OAM beams [34]; (2) Au patch antennas separated from a metal back plane by a MgF\({}_{2}\) spacer are designed and fabricated using the electron-beam evaporation electron-beam lithography technique to realize anomalous reflections [81]; (3) metal H-shaped nano-antenna arrays are designed and fabricated using printed circuit boards to realize high efficiency conversion from propagating waves to surface waves in the microwave regime [82]; (4) metal nanorods are deposited on a glass substrate to generate a hologram [95]; (5) freestanding nanofabricated fishnet metasurfaces are designed and fabricated using the electron-beam lithography method to realize a broadband band pass filter [96]; (6) metal rectangular apertures are arranged in an array with rotational symmetry in metal film to generate OAM beams [98]; (7) metal nanorods are designed and fabricated on glass substrate with a standard electron-beam lithography and lift-off process to generate broadband OAM beams [99]; (8) metal split-ring resonators are designed and fabricated on glass substrate with a standard electron-beam lithography to enhance second harmonic generation [102]. All of these works are based on manipulating the plasmon responses of nano-resonators by altering the dimensions, directions and even arrangement of unit structures. Recently, we have also made some progresses in plasmonic metasurfaces on the basis of previous works. Freestanding nanofabricated fishnet metasurface to function as a broadband band pass filter. Reproduced with permission from [96], Copyright Nature Publishing Group, 2013. \begin{table}
\begin{tabular}{|p{142.3 pt}|p{142.3 pt}|} \hline  & Metal V-shaped nano-antennas to generate optical beams carrying orbital angular momentum (OAM). Reproduced with permission from [34], Copyright The American Association for the Advancement of Science, 2011. \\ \hline  & Au patch antennas separated from a metal back plane by a MgF\({}_{2}\) spacer to realize anomalous reflections. Reproduced with permission from [81], Copyright American Chemical Society, 2012. \\ \hline  & H-shaped microwave nano-antenna arrays to realize high efficiency conversion from propagating waves to surface waves. Reproduced with permission from [82], Copyright Nature Publishing Group, 2012. \\ \hline  & Metal nanorods to generate a hologram. Reproduced with permission from [95], Copyright Nature Publishing Group, 2013. \\ \hline \end{tabular}
\end{table} 
Table 1: Several typical types of plasmonic metasurfaces. Metasurfaces-Based Broadband and Selective Generation of Orbital Angular Momentum Carrying Vector Beams  
Design: We propose and design compact metal-assisted metasurfaces to enable broadband generation of OAM-carrying vector beams. Figure 3a,b depicts the structure and geometric parameters of metal-assisted metasurfaces. We design two concentric rings in a gold film with a thickness of \(h=200\) nm. Each ring is composed of 42 rectangular apertures with gradually-varied orientation. The rectangular aperture array in the gold film can enhance the transmission of linearly-polarized light (perpendicular to the aperture direction), which might be explained as follows: (i) the localized waveguide resonance (each air aperture can be regarded as a truncated rectangular waveguide with four metal walls and two sides open to air); (ii) the property of the surface plasmon resonance due to the aperture array. Hence, each rectangular aperture can be regarded as a localized linear polarizer.