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Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures.

Tian X, Fang Y, Sun M - Sci Rep (2015)

Bottom Line: Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals.However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications.It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule.

View Article: PubMed Central - PubMed

Affiliation: College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan 250014, China.

ABSTRACT
Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule.

No MeSH data available.


Related in: MedlinePlus

Chiral fields formed by different shaped dimers: (a) 40 nm radius Au spheres, (b) 40 nm radius, 30 nm height Au disks and (c) 60 nm (length) × 60 nm (width) × 30 nm (height) Au blocks dimer. The uppermost images in (a–c) show the electric near-field distributions of dimers. The lower two rows of images in (a–c) show the chiral field enhancement distributions of different cut planes. (d–f) Corresponding extinction spectra. The x-y slices are cut from the middle position of height.
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f2: Chiral fields formed by different shaped dimers: (a) 40 nm radius Au spheres, (b) 40 nm radius, 30 nm height Au disks and (c) 60 nm (length) × 60 nm (width) × 30 nm (height) Au blocks dimer. The uppermost images in (a–c) show the electric near-field distributions of dimers. The lower two rows of images in (a–c) show the chiral field enhancement distributions of different cut planes. (d–f) Corresponding extinction spectra. The x-y slices are cut from the middle position of height.

Mentions: The principle discussed above works quite well with many kinds of plasmonic dimers of different shapes. Figure 2 shows the results of Au sphere dimer, disk dimer and block dimer. These three dimers have the same gap distance of 5 nm and similar size. Electromagnetic enhancement and optical chirality of the field in the gap are studied. Optical chirality enhancement is used to characterize the chiral field.


Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures.

Tian X, Fang Y, Sun M - Sci Rep (2015)

Chiral fields formed by different shaped dimers: (a) 40 nm radius Au spheres, (b) 40 nm radius, 30 nm height Au disks and (c) 60 nm (length) × 60 nm (width) × 30 nm (height) Au blocks dimer. The uppermost images in (a–c) show the electric near-field distributions of dimers. The lower two rows of images in (a–c) show the chiral field enhancement distributions of different cut planes. (d–f) Corresponding extinction spectra. The x-y slices are cut from the middle position of height.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664915&req=5

f2: Chiral fields formed by different shaped dimers: (a) 40 nm radius Au spheres, (b) 40 nm radius, 30 nm height Au disks and (c) 60 nm (length) × 60 nm (width) × 30 nm (height) Au blocks dimer. The uppermost images in (a–c) show the electric near-field distributions of dimers. The lower two rows of images in (a–c) show the chiral field enhancement distributions of different cut planes. (d–f) Corresponding extinction spectra. The x-y slices are cut from the middle position of height.
Mentions: The principle discussed above works quite well with many kinds of plasmonic dimers of different shapes. Figure 2 shows the results of Au sphere dimer, disk dimer and block dimer. These three dimers have the same gap distance of 5 nm and similar size. Electromagnetic enhancement and optical chirality of the field in the gap are studied. Optical chirality enhancement is used to characterize the chiral field.

Bottom Line: Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals.However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications.It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule.

View Article: PubMed Central - PubMed

Affiliation: College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan 250014, China.

ABSTRACT
Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule.

No MeSH data available.


Related in: MedlinePlus