Spectroscopy in sculpted fields

Yang, Nan; Tang, Yiqiao; Cohen, Adam E.

doi:10.1016/j.nantod.2009.05.001

Cited by 116 publications

(52 citation statements)

References 87 publications

(89 reference statements)

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“…Circularly polarized lasers produce superhelical electromagnetic fields is chiral objects. 24 That means the change in biomolecular chirality would be amplified when interacting with the circularly polarized laser. Our data reveal that left-handed circularly polarization gives relatively better diagnostic results that do the alternatives.…”

Section: Discussionmentioning

confidence: 99%

Analysis and differentiation of seminal plasma via polarized SERS spectroscopy

Chen¹,

Huang²,

Feng³

et al. 2012

IJN

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Polarized surface-enhanced Raman scattering (SERS) spectroscopy was applied for obtaining biochemical information about the seminal plasma. The effect of different laser polarizations (nonpolarized, linear-polarized, right-handed circularly polarized, and left-handed circularly polarized) on seminal plasma SERS spectroscopy was explored for the first time. The diagnostic performance in differentiating abnormal seminal plasma (n = 37) from normal seminal plasma (n = 24) was evaluated. A combination of principal component analysis (PCA) and linear discriminant analysis (LDA) was employed to develop diagnostic algorithms. Classification results of different laser polarizations demonstrated different diagnostic sensitivities and specificities, among which, left-handed circularly polarized laser excitation showed the best diagnostic result (95.8% sensitivity and 64.9% specificity). Our exploratory study demonstrated that SERS spectroscopy with left-handed circularly polarized laser excitation has the potential for becoming a new diagnostic method in semen-quality assessment.

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Section: Discussionmentioning

confidence: 99%

Analysis and differentiation of seminal plasma via polarized SERS spectroscopy

Chen¹,

Huang²,

Feng³

et al. 2012

IJN

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“…To obtain the near-field generated by the metal tip, we followed standard procedures based on solving the relevant Maxwell equations (SI Materials and Methods). For a sphere of radius and dielectric constant ϵ 1 ðωÞ embedded in an infinite medium of dielectric constant ϵ m ðωÞ and an external field E 0 ðωÞ in the z direction, this equation has a simple solution outside the sphere: ϕ þ ðr; ωÞ ¼ −E 0 ðωÞz 1 − sðωÞ a r 3 [5] and inside the sphere: …”

Section: Methodsmentioning

confidence: 99%

“…The latter is commonly postulated in the form of the electric dipole selection rule (4); however, a range of transitions that are important for spectroscopies such as circular dichroism, Raman scattering, Raman optical activity, singlet-triplet transitions, and magneto-optical phenomena are forbidden in an electric far-field. Common examples include electric quadrupole (q), magnetic dipole (m), and coupled electric dipole-magnetic dipole excitations (μ·m) (2,5).By the use of nanostructures (6-9), photonic crystals (10), or complex laser interference excitation schemes (11, 12), it is possible to engineer electromagnetic fields of light with spatial variations on the nanoscale approaching molecular length scales and to achieve optical phenomena beyond those allowed by conventional far-fields (13, 14). Jain et al showed that magneto-optical Faraday rotation of a magnetic nanocrystal could be resonantly enhanced by placing it within the near-field of a plasmonic nanoshell, possibly via enhancement of the quadrupolar and μ·m transitions in the strongly graded electric field near the nanostructure (9).…”

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confidence: 99%

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confidence: 99%

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Near-field manipulation of spectroscopic selection rules on the nanoscale

Jain

Ghosh

Baer

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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In conventional spectroscopy, transitions between electronic levels are governed by the electric dipole selection rule because electric quadrupole, magnetic dipole, and coupled electric dipole-magnetic dipole transitions are forbidden in a far field. We demonstrated that by using nanostructured electromagnetic fields, the selection rules of absorption spectroscopy could be fundamentally manipulated. We also show that forbidden transitions between discrete quantum levels in a semiconductor nanorod structure are allowed within the near-field of a noble metal nanoparticle. Atomistic simulations analyzed by an effective mass model reveal the breakdown of the dipolar selection rules where quadrupole and octupole transitions are allowed. Our demonstration could be generalized to the use of nanostructured near-fields for enhancing light-matter interactions that are typically weak or forbidden.absorption spectra | plasmonics | quantum dot | exciton L ight-matter interactions that govern most forms of spectroscopy, light harvesting, optical imaging, photodetection, optical communications, and data storage are conceptually founded on the laws of far-field optics (1, 2). Electronic and vibrational transitions excited by the electromagnetic (EM) field of light involve the motion of electrons and atoms on the length scale of 1 Å, the typical size of a molecule. Because the size (r) of a molecule is 10 3 times smaller than the wavelength (λ) of the light, it is common to approximate that a molecule subjected to light experiences a uniform electric field (1, 2). Spatial variations of this field across the molecule are neglected in the far-field limit. In this limit, the electric field can excite only those transitions that involve the induction of an electric dipole moment across the molecule, which is assumed to be a point (3). The latter is commonly postulated in the form of the electric dipole selection rule (4); however, a range of transitions that are important for spectroscopies such as circular dichroism, Raman scattering, Raman optical activity, singlet-triplet transitions, and magneto-optical phenomena are forbidden in an electric far-field. Common examples include electric quadrupole (q), magnetic dipole (m), and coupled electric dipole-magnetic dipole excitations (μ·m) (2,5).By the use of nanostructures (6-9), photonic crystals (10), or complex laser interference excitation schemes (11, 12), it is possible to engineer electromagnetic fields of light with spatial variations on the nanoscale approaching molecular length scales and to achieve optical phenomena beyond those allowed by conventional far-fields (13, 14). Jain et al. showed that magneto-optical Faraday rotation of a magnetic nanocrystal could be resonantly enhanced by placing it within the near-field of a plasmonic nanoshell, possibly via enhancement of the quadrupolar and μ·m transitions in the strongly graded electric field near the nanostructure (9). Tang and Cohen (11,12) recently showed that at the nodes of a standing wave of circularly polarized light...

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“…Recently, prototype nanocircuits using gap nanoantennas [5,6] in connection with plasmonic two-wire transmission lines (TWTLs) have been theoretically proposed [7][8][9] and experimentally studied [10][11][12], showing a realizable approach to the manipulation of electromagnetic field for enhanced spectroscopy [13,14].…”

Section: Introductionmentioning

confidence: 99%

Plasmonic mode converter for controlling optical impedance and nanoscale light-matter interaction

Hung

Huang

2012

Opt. Express

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Abstract:To enable multiple functions of plasmonic nanocircuits, it is of key importance to control the propagation properties and the modal distribution of the guided optical modes such that their impedance matches to that of nearby quantum systems and desired light-matter interaction can be achieved. Here, we present efficient mode converters for manipulating guided modes on a plasmonic two-wire transmission line. The mode conversion is achieved through varying the path length, wire cross section and the surrounding index of refraction. Instead of pure optical interference, strong near-field coupling of surface plasmons results in great momentum splitting and modal profile variation. We theoretically demonstrate control over nanoantenna radiation and discuss the possibility to enhance nanoscale light-matter interaction. The proposed converter may find applications in surface plasmon amplification, index sensing and enhanced nanoscale spectroscopy.

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Spectroscopy in sculpted fields

Cited by 116 publications

References 87 publications

Analysis and differentiation of seminal plasma via polarized SERS spectroscopy

Analysis and differentiation of seminal plasma via polarized SERS spectroscopy

Near-field manipulation of spectroscopic selection rules on the nanoscale

Plasmonic mode converter for controlling optical impedance and nanoscale light-matter interaction

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