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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.


Electric field intensity verse wavelength for the structures with concentric rings for different dielectric layer thickness. The field intensities at the middle of the gap of the DERS structure with concentric rings with periodicity of ring P = 650 nm and dielectric layer thicknesses of 20, 25, 30, 40, 50, and 60 nm.
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Fig5: Electric field intensity verse wavelength for the structures with concentric rings for different dielectric layer thickness. The field intensities at the middle of the gap of the DERS structure with concentric rings with periodicity of ring P = 650 nm and dielectric layer thicknesses of 20, 25, 30, 40, 50, and 60 nm.

Mentions: To understand the effects of the dielectric layer thickness on the near-field enhancements and far-field radiation, Figure 5 shows the simulation results of the electric field at the center of the nanoantenna for the DERS structure with concentric rings with different dielectric layer thicknesses ranging from H = 20 nm to H = 60 nm. The periodicity of P = 650 nm is fixed. The peaks between λ = 850 nm and λ = 950 nm shift when the dielectric layer thickness is changed. It is because the light coupling efficiency from the gold rings to the nanoantenna can be affected by the dielectric layer thickness. The peaks between λ = 600 nm and λ = 750 nm are strongly dependent on the dielectric material thickness, and the field enhancement of these peaks becomes larger as the dielectric layer thickness is smaller. The electric field in the dielectric layer can be interfered between the gold rings and bottom gold layer because the light can go back and forth between them. Thus, the large field enhancement can be achieved as the constructive interference happens by choosing a suitable layer thickness, such as the case with H = 20 nm in Figure 5.Figure 5


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)

Electric field intensity verse wavelength for the structures with concentric rings for different dielectric layer thickness. The field intensities at the middle of the gap of the DERS structure with concentric rings with periodicity of ring P = 650 nm and dielectric layer thicknesses of 20, 25, 30, 40, 50, and 60 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig5: Electric field intensity verse wavelength for the structures with concentric rings for different dielectric layer thickness. The field intensities at the middle of the gap of the DERS structure with concentric rings with periodicity of ring P = 650 nm and dielectric layer thicknesses of 20, 25, 30, 40, 50, and 60 nm.
Mentions: To understand the effects of the dielectric layer thickness on the near-field enhancements and far-field radiation, Figure 5 shows the simulation results of the electric field at the center of the nanoantenna for the DERS structure with concentric rings with different dielectric layer thicknesses ranging from H = 20 nm to H = 60 nm. The periodicity of P = 650 nm is fixed. The peaks between λ = 850 nm and λ = 950 nm shift when the dielectric layer thickness is changed. It is because the light coupling efficiency from the gold rings to the nanoantenna can be affected by the dielectric layer thickness. The peaks between λ = 600 nm and λ = 750 nm are strongly dependent on the dielectric material thickness, and the field enhancement of these peaks becomes larger as the dielectric layer thickness is smaller. The electric field in the dielectric layer can be interfered between the gold rings and bottom gold layer because the light can go back and forth between them. Thus, the large field enhancement can be achieved as the constructive interference happens by choosing a suitable layer thickness, such as the case with H = 20 nm in Figure 5.Figure 5

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.