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Electric field enhancement and far-field radiation pattern of the nanoantenna with concentric rings.

Chen SW, Huang YH, Chao BK, Hsueh CH, Li JH - Nanoscale Res Lett (2014)

Bottom Line: The directivity of a dipole antenna can be improved by directivity-enhanced Raman scattering structure, which is a combination of a dipole antenna and a ring reflector layer on a ground plane.The measured results show that the structure with concentric rings can have stronger SERS signals.The proposed structure can be useful for several nanoantenna applications, such as sensing or detecting.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei, 10617, Taiwan, shihwenc@gmail.com.

ABSTRACT
The optical antennas have the potential in various applications because of their field enhancement and directivity control. The directivity of a dipole antenna can be improved by directivity-enhanced Raman scattering structure, which is a combination of a dipole antenna and a ring reflector layer on a ground plane. The concentric rings can collect the light into the center hole. Depending upon the geometry of the antenna inside the hole, different electric field enhancements can be achieved. In this paper, we propose to combine the concentric rings with the directivity-enhanced Raman scattering structure in order to study its electric field enhancement and the far-field radiation pattern by finite-difference time-domain simulations. Compared with the structure without the concentric rings over the ground plane, it is found that our proposed structure can obtain stronger electric field enhancements and narrower radiation beams because the gold rings can help to couple the light into the nanoantenna and they also scatter light into the far field and modify the far-field radiation pattern. The designed structures were fabricated and the chemical molecules of thiophenol were attached on the structures for surface-enhanced Raman scattering (SERS) measurements. The measured results show that the structure with concentric rings can have stronger SERS signals. The effects of the dielectric layer thickness in our proposed structure on the near-field enhancements and far-field radiation are also investigated. The proposed structure can be useful for several nanoantenna applications, such as sensing or detecting.

No MeSH data available.


Far-field radiation patterns for the structures with and without the concentric rings. (a) The DERS structure and (b) the structure with concentric rings at λ = 880 nm. The radiation pattern is calculated from the simulations by placing an x-polarized electric dipole source at the feed gap of the dipole antenna.
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Fig4: Far-field radiation patterns for the structures with and without the concentric rings. (a) The DERS structure and (b) the structure with concentric rings at λ = 880 nm. The radiation pattern is calculated from the simulations by placing an x-polarized electric dipole source at the feed gap of the dipole antenna.

Mentions: To study the far-field radiation pattern by the nanoantenna in the DESR structure with and without concentric rings, we assume that an x-polarized electric dipole source is placed at the feed gap of the dipole antenna and calculate the far-field radiations in our simulations. Figure 4a,b shows the far-field radiation pattern for the DERS structure without and with concentric rings, respectively, at λ = 880 nm. It is obvious that the radiation beam is narrower for the case with concentric rings in Figure 4b than the case without concentric rings in Figure 4a. The narrower far-field radiation beam can be explained by the contributions of the gold rings which can also scatter light into far field and modify the far-field radiation pattern. It can be helpful for some applications which need to control the light beam scattering directivity, for example, the molecule detection by surface-enhanced Raman scattering.Figure 4


Electric field enhancement and far-field radiation pattern of the nanoantenna with concentric rings.

Chen SW, Huang YH, Chao BK, Hsueh CH, Li JH - Nanoscale Res Lett (2014)

Far-field radiation patterns for the structures with and without the concentric rings. (a) The DERS structure and (b) the structure with concentric rings at λ = 880 nm. The radiation pattern is calculated from the simulations by placing an x-polarized electric dipole source at the feed gap of the dipole antenna.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494036&req=5

Fig4: Far-field radiation patterns for the structures with and without the concentric rings. (a) The DERS structure and (b) the structure with concentric rings at λ = 880 nm. The radiation pattern is calculated from the simulations by placing an x-polarized electric dipole source at the feed gap of the dipole antenna.
Mentions: To study the far-field radiation pattern by the nanoantenna in the DESR structure with and without concentric rings, we assume that an x-polarized electric dipole source is placed at the feed gap of the dipole antenna and calculate the far-field radiations in our simulations. Figure 4a,b shows the far-field radiation pattern for the DERS structure without and with concentric rings, respectively, at λ = 880 nm. It is obvious that the radiation beam is narrower for the case with concentric rings in Figure 4b than the case without concentric rings in Figure 4a. The narrower far-field radiation beam can be explained by the contributions of the gold rings which can also scatter light into far field and modify the far-field radiation pattern. It can be helpful for some applications which need to control the light beam scattering directivity, for example, the molecule detection by surface-enhanced Raman scattering.Figure 4

Bottom Line: The directivity of a dipole antenna can be improved by directivity-enhanced Raman scattering structure, which is a combination of a dipole antenna and a ring reflector layer on a ground plane.The measured results show that the structure with concentric rings can have stronger SERS signals.The proposed structure can be useful for several nanoantenna applications, such as sensing or detecting.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei, 10617, Taiwan, shihwenc@gmail.com.

ABSTRACT
The optical antennas have the potential in various applications because of their field enhancement and directivity control. The directivity of a dipole antenna can be improved by directivity-enhanced Raman scattering structure, which is a combination of a dipole antenna and a ring reflector layer on a ground plane. The concentric rings can collect the light into the center hole. Depending upon the geometry of the antenna inside the hole, different electric field enhancements can be achieved. In this paper, we propose to combine the concentric rings with the directivity-enhanced Raman scattering structure in order to study its electric field enhancement and the far-field radiation pattern by finite-difference time-domain simulations. Compared with the structure without the concentric rings over the ground plane, it is found that our proposed structure can obtain stronger electric field enhancements and narrower radiation beams because the gold rings can help to couple the light into the nanoantenna and they also scatter light into the far field and modify the far-field radiation pattern. The designed structures were fabricated and the chemical molecules of thiophenol were attached on the structures for surface-enhanced Raman scattering (SERS) measurements. The measured results show that the structure with concentric rings can have stronger SERS signals. The effects of the dielectric layer thickness in our proposed structure on the near-field enhancements and far-field radiation are also investigated. The proposed structure can be useful for several nanoantenna applications, such as sensing or detecting.

No MeSH data available.