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Demonstration of a Three-dimensional Negative Index Medium Operated at Multiple-angle Incidences by Monolithic Metallic Hemispherical Shells

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ABSTRACT

We design and construct a three-dimensional (3D) negative index medium (NIM) composed of gold hemispherical shells to supplant an integration of a split-ring resonator and a discrete plasmonic wire for both negative permeability and permittivity at THz gap. With the proposed highly symmetric gold hemispherical shells, the negative index is preserved at multiple incident angles ranging from 0° to 85° for both TE and TM waves, which is further evidenced by negative phase flows in animated field distributions and outweighs conventional fishnet structures with operating frequency shifts when varying incident angles. Finally, the fabrication of the gold hemispherical shells is facilitated via standard UV lithographic and isotropic wet etching processes and characterized by μ-FTIR. The measurement results agree the simulated ones very well.

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Phase flows within free space and five-layered 3D NIM under oblique incidence.Simulated transmission spectra of five-layered 3D NIMs under 0°, 15° and 30° incidences for (a) TE and (d) TM cases. The animated phases of magnetic fields under (b) 15° incidence at 1.134 THz and (c) 30° incidence at 1.081 THz and the animated phases of electric fields under (e) 15° incidence and (f) 30° incidence both at 1.185 THz are presented. In order to clarify the wave propagating direction, we monitor different fields, magnetic fields for TE case and electric fields for TM case so that the phase of fields could be plane-wave-like. The upper to lower frames in (b,c) to (e,f) are all with a constant step of phase change, i.e., 50-degree, and white arrows indicate the wave propagation direction in free space while red arrows in five-layered 3D NIM. The two are opposite and suggest the double negative identities of the 3D NIM.
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f6: Phase flows within free space and five-layered 3D NIM under oblique incidence.Simulated transmission spectra of five-layered 3D NIMs under 0°, 15° and 30° incidences for (a) TE and (d) TM cases. The animated phases of magnetic fields under (b) 15° incidence at 1.134 THz and (c) 30° incidence at 1.081 THz and the animated phases of electric fields under (e) 15° incidence and (f) 30° incidence both at 1.185 THz are presented. In order to clarify the wave propagating direction, we monitor different fields, magnetic fields for TE case and electric fields for TM case so that the phase of fields could be plane-wave-like. The upper to lower frames in (b,c) to (e,f) are all with a constant step of phase change, i.e., 50-degree, and white arrows indicate the wave propagation direction in free space while red arrows in five-layered 3D NIM. The two are opposite and suggest the double negative identities of the 3D NIM.

Mentions: Next, we record the phase flow of within the 3D NIM under the oblique incident cases and exemplify the negative index at 15° and 30° incident angles for both TE and TM cases. The transmission spectra and animated phases of the five-layered 3D NIM at 15° and 30° incidences are portrayed in Fig. 6(a–c) for the TE case, and Fig. 6(d–f) for the TM cases. The simulated transmission spectra (see Fig. 6(a,d)) of the five-layered 3D NIM display a red shift of the transmission peaks for the TE case but stay almost unaltered for the TM case from normal to 30° incidence that is consistent with the trend of the single-layered 3D NIM. In the following phase flow demonstration, we monitor different fields, magnetic fields for the TE case and electric fields for the TM case so that phases of the fields could be plane-wave-like to be clearly observed. Figure 6(b,c) show the snapshots of the animated phases for the transmission apexes at 1.134 THz and at 1.081 THz at 15° and 30° incidences, respectively for the TE case; Fig. 6(e,f) display the flows at the frequency of 1.185 THz under the two incidences for the TM case. Within all the consecutive snapshots of the animated phases from the upper to lower frames, the wave propagation directions in free space (white arrows) and in the five-layered 3D NIM (red arrows) evidently reveal opposite phase flows to corroborate the negative index.


Demonstration of a Three-dimensional Negative Index Medium Operated at Multiple-angle Incidences by Monolithic Metallic Hemispherical Shells
Phase flows within free space and five-layered 3D NIM under oblique incidence.Simulated transmission spectra of five-layered 3D NIMs under 0°, 15° and 30° incidences for (a) TE and (d) TM cases. The animated phases of magnetic fields under (b) 15° incidence at 1.134 THz and (c) 30° incidence at 1.081 THz and the animated phases of electric fields under (e) 15° incidence and (f) 30° incidence both at 1.185 THz are presented. In order to clarify the wave propagating direction, we monitor different fields, magnetic fields for TE case and electric fields for TM case so that the phase of fields could be plane-wave-like. The upper to lower frames in (b,c) to (e,f) are all with a constant step of phase change, i.e., 50-degree, and white arrows indicate the wave propagation direction in free space while red arrows in five-layered 3D NIM. The two are opposite and suggest the double negative identities of the 3D NIM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC5384282&req=5

f6: Phase flows within free space and five-layered 3D NIM under oblique incidence.Simulated transmission spectra of five-layered 3D NIMs under 0°, 15° and 30° incidences for (a) TE and (d) TM cases. The animated phases of magnetic fields under (b) 15° incidence at 1.134 THz and (c) 30° incidence at 1.081 THz and the animated phases of electric fields under (e) 15° incidence and (f) 30° incidence both at 1.185 THz are presented. In order to clarify the wave propagating direction, we monitor different fields, magnetic fields for TE case and electric fields for TM case so that the phase of fields could be plane-wave-like. The upper to lower frames in (b,c) to (e,f) are all with a constant step of phase change, i.e., 50-degree, and white arrows indicate the wave propagation direction in free space while red arrows in five-layered 3D NIM. The two are opposite and suggest the double negative identities of the 3D NIM.
Mentions: Next, we record the phase flow of within the 3D NIM under the oblique incident cases and exemplify the negative index at 15° and 30° incident angles for both TE and TM cases. The transmission spectra and animated phases of the five-layered 3D NIM at 15° and 30° incidences are portrayed in Fig. 6(a–c) for the TE case, and Fig. 6(d–f) for the TM cases. The simulated transmission spectra (see Fig. 6(a,d)) of the five-layered 3D NIM display a red shift of the transmission peaks for the TE case but stay almost unaltered for the TM case from normal to 30° incidence that is consistent with the trend of the single-layered 3D NIM. In the following phase flow demonstration, we monitor different fields, magnetic fields for the TE case and electric fields for the TM case so that phases of the fields could be plane-wave-like to be clearly observed. Figure 6(b,c) show the snapshots of the animated phases for the transmission apexes at 1.134 THz and at 1.081 THz at 15° and 30° incidences, respectively for the TE case; Fig. 6(e,f) display the flows at the frequency of 1.185 THz under the two incidences for the TM case. Within all the consecutive snapshots of the animated phases from the upper to lower frames, the wave propagation directions in free space (white arrows) and in the five-layered 3D NIM (red arrows) evidently reveal opposite phase flows to corroborate the negative index.

View Article: PubMed Central - PubMed

ABSTRACT

We design and construct a three-dimensional (3D) negative index medium (NIM) composed of gold hemispherical shells to supplant an integration of a split-ring resonator and a discrete plasmonic wire for both negative permeability and permittivity at THz gap. With the proposed highly symmetric gold hemispherical shells, the negative index is preserved at multiple incident angles ranging from 0° to 85° for both TE and TM waves, which is further evidenced by negative phase flows in animated field distributions and outweighs conventional fishnet structures with operating frequency shifts when varying incident angles. Finally, the fabrication of the gold hemispherical shells is facilitated via standard UV lithographic and isotropic wet etching processes and characterized by μ-FTIR. The measurement results agree the simulated ones very well.

No MeSH data available.


Related in: MedlinePlus