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Vertical split-ring resonator based anomalous beam steering with high extinction ratio.

Hsu WL, Wu PC, Chen JW, Chen TY, Cheng BH, Chen WT, Huang YW, Liao CY, Sun G, Tsai DP - Sci Rep (2015)

Bottom Line: Limited by nanofabrication difficulties, so far most reported works have been based on 2D metal structures.We have recently developed an advanced e-beam process that allowed for the deposition of 3D nanostructures, namely vertical split-ring resonators (VSRRs), which opens up another degree of freedom in the metasurface design.We also demonstrate that metasurfaces made of 3D VSRRs can be made with roughly half of the footprint compared to that of 2D nano-rods, enabling high density integration of metal nanostructures.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Taiwan University, Taipei 10617, Taiwan.

ABSTRACT
Metasurfaces created artificially with metal nanostructures that are patterned on surfaces of different media have shown to possess "unusual" abilities to manipulate light. Limited by nanofabrication difficulties, so far most reported works have been based on 2D metal structures. We have recently developed an advanced e-beam process that allowed for the deposition of 3D nanostructures, namely vertical split-ring resonators (VSRRs), which opens up another degree of freedom in the metasurface design. Here we explore the functionality of beam steering with phase modulation by tuning only the vertical dimension of the VSRRs and show that anomalous steering reflection of a wide range of angles can be accomplished with high extinction ratio using the finite-difference-time-domain simulation. We also demonstrate that metasurfaces made of 3D VSRRs can be made with roughly half of the footprint compared to that of 2D nano-rods, enabling high density integration of metal nanostructures.

No MeSH data available.


Schematic of VSRR-based metasurface.(a) Schematic of a unit cell consisting of 18 VSRR of equal base but six different prong heights: 30, 60, 90, 120, 150, and 0 nm, with three VSRRs of equal dimensions. Each unit cell occupies Lx = 2160 nm and Ly = 250 nm. (b) Illustration of the VSRR-based metasurface beam steering.
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f2: Schematic of VSRR-based metasurface.(a) Schematic of a unit cell consisting of 18 VSRR of equal base but six different prong heights: 30, 60, 90, 120, 150, and 0 nm, with three VSRRs of equal dimensions. Each unit cell occupies Lx = 2160 nm and Ly = 250 nm. (b) Illustration of the VSRR-based metasurface beam steering.

Mentions: We subsequently use these VSRRs of six different heights to construct a unit cell with the necessary period to steer a normal incident beam of a particular wavelength onto a pre-determined angle. Figure 2(a) shows the schematic of a VSRR based unit cell occupying an area of Lx × Ly = 2160 × 250 nm2. Such a unit cell is repeated along x- and y-directions to form the functional metasurface where the long period of 2160 nm is chosen to yield a steering angle of 45° for the normal incident light of λ = 1548 nm as shown in Fig. 2(b). It takes 18 VSRRs to fill up a unit cell (Fig. 2(a)) in which six sets of three VSRRs of same height are arranged to obtain the phase modulations in Fig. 1(d). In order for a normal incident beam to be redirected to 45° (Fig. 2(b)) according to the generalized Snell’s law, the amount of in-plane wave-vector that needs to be provided by the metasurface is where is the wavevector in free space. It follows then that such a metasurface will also steer light with an arbitrary incident angle θi to the reflection angle θr according to .


Vertical split-ring resonator based anomalous beam steering with high extinction ratio.

Hsu WL, Wu PC, Chen JW, Chen TY, Cheng BH, Chen WT, Huang YW, Liao CY, Sun G, Tsai DP - Sci Rep (2015)

Schematic of VSRR-based metasurface.(a) Schematic of a unit cell consisting of 18 VSRR of equal base but six different prong heights: 30, 60, 90, 120, 150, and 0 nm, with three VSRRs of equal dimensions. Each unit cell occupies Lx = 2160 nm and Ly = 250 nm. (b) Illustration of the VSRR-based metasurface beam steering.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4459221&req=5

f2: Schematic of VSRR-based metasurface.(a) Schematic of a unit cell consisting of 18 VSRR of equal base but six different prong heights: 30, 60, 90, 120, 150, and 0 nm, with three VSRRs of equal dimensions. Each unit cell occupies Lx = 2160 nm and Ly = 250 nm. (b) Illustration of the VSRR-based metasurface beam steering.
Mentions: We subsequently use these VSRRs of six different heights to construct a unit cell with the necessary period to steer a normal incident beam of a particular wavelength onto a pre-determined angle. Figure 2(a) shows the schematic of a VSRR based unit cell occupying an area of Lx × Ly = 2160 × 250 nm2. Such a unit cell is repeated along x- and y-directions to form the functional metasurface where the long period of 2160 nm is chosen to yield a steering angle of 45° for the normal incident light of λ = 1548 nm as shown in Fig. 2(b). It takes 18 VSRRs to fill up a unit cell (Fig. 2(a)) in which six sets of three VSRRs of same height are arranged to obtain the phase modulations in Fig. 1(d). In order for a normal incident beam to be redirected to 45° (Fig. 2(b)) according to the generalized Snell’s law, the amount of in-plane wave-vector that needs to be provided by the metasurface is where is the wavevector in free space. It follows then that such a metasurface will also steer light with an arbitrary incident angle θi to the reflection angle θr according to .

Bottom Line: Limited by nanofabrication difficulties, so far most reported works have been based on 2D metal structures.We have recently developed an advanced e-beam process that allowed for the deposition of 3D nanostructures, namely vertical split-ring resonators (VSRRs), which opens up another degree of freedom in the metasurface design.We also demonstrate that metasurfaces made of 3D VSRRs can be made with roughly half of the footprint compared to that of 2D nano-rods, enabling high density integration of metal nanostructures.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Taiwan University, Taipei 10617, Taiwan.

ABSTRACT
Metasurfaces created artificially with metal nanostructures that are patterned on surfaces of different media have shown to possess "unusual" abilities to manipulate light. Limited by nanofabrication difficulties, so far most reported works have been based on 2D metal structures. We have recently developed an advanced e-beam process that allowed for the deposition of 3D nanostructures, namely vertical split-ring resonators (VSRRs), which opens up another degree of freedom in the metasurface design. Here we explore the functionality of beam steering with phase modulation by tuning only the vertical dimension of the VSRRs and show that anomalous steering reflection of a wide range of angles can be accomplished with high extinction ratio using the finite-difference-time-domain simulation. We also demonstrate that metasurfaces made of 3D VSRRs can be made with roughly half of the footprint compared to that of 2D nano-rods, enabling high density integration of metal nanostructures.

No MeSH data available.