Hyper-Raman scattering enhanced by anisotropic dimer plasmons on artificial nanostructures

Abstract

Silver nanodimers with a small gap of a few nanometers aligned on glass substrates were used to enhance hyper-Raman scattering of crystal violet dye molecules. When localized surface plasmon of the dimer array was resonantly excited along the interparticle axis, hyper-Raman intensity was significantly enhanced. Moreover, the spectral appearance was slightly different between the two excitation polarizations, suggesting a possibility of two resonance contributions at one-photon and two-photon energies. Since the plasmonic property of dimer arrays can be controlled by the dimer geometry, the dimer arrays are expected to be well-defined substrates for surface-enhanced hyper-Raman spectroscopy

Interpretation of the spectra of surface-enhanced hyper-Raman scattering of symmetric molecules, based on dipole–quadrupole theory

“…We should point out that a careful consideration of the experimentally measured and calculated lines, the vibrational wavenumbers, and the possible assignment of the vibrations to various irreducible representations revealed large discrepancies in the computed values and the determination of the vibrational symmetry assigned to the individual lines (see Refs. [10][11][12][13]. Therefore, our attempts to make our own correlation of the enhanced Hyper-RS lines turned out to be unsuccessful, and we assume that the question of accurate correlation is at present questionable.…”

Surface enhanced hyper Raman scattering (SEHRS) and its applications

“…64 In addition, fabrication of welldefined structures with nanoscale gaps, commonly used in SERS, [97][98][99] has also been implemented in SEHRS. 69 Anisotropic silver dimer arrays were the first artificially designed nanostructures employed in SEHRS measurements. 69 However, relatively little work has been done in this direction for SEHRS and further optimization of the electromagnetic enhancement should be possible.…”

“…69 Anisotropic silver dimer arrays were the first artificially designed nanostructures employed in SEHRS measurements. 69 However, relatively little work has been done in this direction for SEHRS and further optimization of the electromagnetic enhancement should be possible.…”

“…10,[22][23][24]42,44,60,68 A few groups report SEHRS spectra on immobilized or lithographically fabricated nanostructures. 64,69 As a first real biological application, SEHRS spectra were collected to analyze intrinsic biochemical information from nanometer-scaled volumes in dry-fixed individual culture cells. 17,70 Furthermore, using a CW laser at 1064 nm (B300 mW average power) SEHRS was combined with the optical trapping of nanoaggregates, and spectra of dye molecules were obtained under resonant conditions.…”

“…In agreement with this, for example, an energy of only 2-8 pJ (a few hundred mW) provided by a mode-locked Ti:Sa laser is sufficient to record resonant SEHRS spectra of various chromophores. 61,69,86,88,89 On the other hand, at an excitation wavelength around 1064 nm, the required intensities are higher, especially under off-resonant conditions, where typically average powers between 10 mW and a few 100 mW are used, leading to intensities in the range of 10 8 -10 10 W cm À2 depending on the repetition rate and pulse duration of the laser. As …”