Direct phase mapping of the light scattered by single plasmonic nanoparticles

Abstract

KEYWORDS (Word Style "BG_Keywords"). If you are submitting your paper to a journal that requires keywords, provide significant keywords to aid the reader in literature retrieval.In this work, we present a novel technique to directly measure the phase shift of the optical signal scattered by single plasmonic nanoparticles in a diffraction-limited laser focus. We accomplish this by equipping an inverted confocal microscope with a Michelson interferometer and scanning single nanoparticles through the focal volume while recording interferograms of the scattered and a reference wave for each pixel. For the experiments, lithographically prepared gold nanorods where used, since their plasmon resonances can be controlled via their aspect ratio. We have developed a theoretical model for image formation in confocal scattering microscopy for nanoparticles considerably smaller than the diffraction limited focus We show that the phase shift observed for particles with different longitudinal particle plasmon resonances can be well explained by the harmonic oscillator model. The direct measurement of the phase shift can further improve the understanding of the elastic scattering of individual gold nanoparticles with respect to their plasmonic properties.

The Generation and Study of a Gold‐Based Chemobrionic Plant‐Like Structure

“…Τhe energy of this band is at 15523.8 cm −1 ( em = 0 ‐ Rs , where 0 is the wavenumber of the incident laser light and Rs the wavenumber of the band which appears in the Stokes side of Raman spectrum) that corresponds to 644.2 nm. Emission bands with similar energy have been observed when exciting gold nanostructures with the excitation line 632.8 nm that we also used [18] . As it has been reported before, [19] laser induced dissociation/reduction of the colored Au 2 Cl 6 vapors by the absorbed laser line resulted to solid deposits (Au and/or AuCl) that obscured the Raman spectra [19] …”

“…Emission bands with similar energy have been observed when exciting gold nanostructures with the excitation line 632.8 nm that we also used. [18] As it has been reported before, [19] laser induced dissociation/reduction of the colored Au 2 Cl 6 vapors by the absorbed laser line resulted to solid deposits (Au and/or AuCl) that obscured the Raman spectra. [19] In conclusion, in the present study, we have studied the generation and growth of gold-based chemical gardens.…”

“…While recording micro‐Raman spectra the laser power was kept low (0.3 mW on the sample) and the accumulation time short (2 min) in order to avoid spectral changes due to heat‐induced effects, observed in Figure 4 (spectra (b)), where a new strong peak appears at 279 cm −1 . A possible explanation is that this intense band can be attributed to an emission/scattering, probably from gold nanostructures [18] formed due to laser induced dissociation of the Au(III) compounds after prolonged exposure of the sample to laser radiation. Τhe energy of this band is at 15523.8 cm −1 ( em = 0 ‐ Rs , where 0 is the wavenumber of the incident laser light and Rs the wavenumber of the band which appears in the Stokes side of Raman spectrum) that corresponds to 644.2 nm.…”

Revealing the Three-Dimensional Orientation and Interplay between Plasmons and Interband Transitions for Single Gold Bipyramids by Photoluminescence Excitation Pattern Imaging

“…In most cases, white-light scattering is used to characterize the plasmonic properties of nanostructures. Scattering-based methods, such as defocused dark-field imaging, back focal plane imaging, interferometric scattering microscopy, , and direct phase mapping are utilized to distinguish the geometrical properties of nanoparticles. However, scattering methods suffer from a scattering background that originates from impurities and interfaces, which is especially problematic in biological applications.…”

One-Shot Phase Image Distinction of Plasmonic and Dielectric Nanoparticles

“…Since these pioneering works, technology has advanced rapidly, and different phase-detecting techniques are of crucial importance across many scientific fields. In nanoscale physics, the phase of a nanoparticle (NP) accesses its nanoscale response − and is a crucial parameter for tailoring complex photonic structures such as metasurfaces which manipulate the amplitude, direction, and polarization of light at nano- to microscales. , In the biomedical sciences, phase-based measurements are often key enablers for ultrasensitive measurements such as protein-binding to plasmonic structures, − and the emerging field of quantitative phase imaging is expected to dramatically contribute to future diagnostics. , …”