Исследование диэлектрических функций слоя наночастиц Ag на кремнии с помощью спектроэллипсометрии и спектрофотометрии

An investigation of the optical characteristics of a layer of Ag nanoparticles deposited from an AgNO3 solution on the surface of single-crystal Si is presented. The measurements were carried out using spectroscopic ellipsometry and spectrophotometry at the same tilt angle and sample probe location in a wide spectral range from 200 to 1700 nm. From the obtained experimental data, the parameters of the Drude-Lorentz model and the complex dielectric function were determined, which was compared with the pseudo-dielectric function. Both dependences revealed resonances of a bulk plasmon near the energy E = 3.8 eV, while a localized plasmon was detected in the pseudo-dielectric function at E = 1.65 eV, and in the dielectric function at E = 1.84 eV.

Synthesis of prolate gold nanoparticles for use in plasmon-enhanced overtone near-infrared spectroscopy

Gold nanoparticles were obtained by the method of three-stage growth from a seed solution. Scanning electron microscopy images as well as comparison of extinction spectra to the results of numerical simulations prove the formation of prolate nanoparticles. Such particles with localized plasmon resonance in the NIR region are much-needed for the plasmon-enhanced overtone spectroscopy.

Tip-enhanced Stokes and anti-Stokes Raman scattering in defect-enriched carbon films

Anti-Stokes Raman scattering is one of the mechanisms that lie behind an optical refrigeration due to release of photons with greater energy than of incoming photons. To achieve a cooling regime the enhancement of anti-Stokes scattering is necessary, since spontaneous Stokes scattering dominates over anti-Stokes scattering under normal conditions. Here, we investigate the opportunity of enhancement of spontaneous anti-Stokes Raman scattering in defect-enriched carbon film by means of localized plasmon resonances. In our simulations, incoherence of Raman scattering results in excess of anti-Stokes intensity over Stokes one. However, when the field is localized within the phonon coherence volume (coherent regime), the anti-Stokes intensity is lower compared to Stokes one. The provided analysis shows that plasmon-enhanced anti-Stokes Raman scattering can be achieved in highly-defective carbon films. The results are beneficial for Raman-based temperature measurements on the nanoscale.

Double moiré localized plasmon structured illumination microscopy

Structured illumination microscopy (SIM) is a well-established fluorescence imaging technique, which can increase spatial resolution by up to a factor of two. This article reports on a new way to extend the capabilities of structured illumination microscopy, by combining ideas from the fields of illumination engineering and nanophotonics. In this technique, plasmonic arrays of hexagonal symmetry are illuminated by two obliquely incident beams originating from a single laser. The resulting interference between the light grating and plasmonic grating creates a wide range of spatial frequencies above the microscope passband, while still preserving the spatial frequencies of regular SIM. To systematically investigate this technique and to contrast it with regular SIM and localized plasmon SIM, we implement a rigorous simulation procedure, which simulates the near-field illumination of the plasmonic grating and uses it in the subsequent forward imaging model. The inverse problem, of obtaining a super-resolution (SR) image from multiple low-resolution images, is solved using a numerical reconstruction algorithm while the obtained resolution is quantitatively assessed. The results point at the possibility of resolution enhancements beyond regular SIM, which rapidly vanishes with the height above the grating. In an initial experimental realization, the existence of the expected spatial frequencies is shown and the performance of compatible reconstruction approaches is compared. Finally, we discuss the obstacles of experimental implementations that would need to be overcome for artifact-free SR imaging.

Bideposited silver nanocolloid arrays with strong plasmon-induced birefringence for SERS application

Silver nano-rod, nano-zigzag, nano-saw, and nano-particle arrays are fabricated with glancing angle bideposition. The structure-dependent anisotropic optical properties of those bideposited nanostructured arrays are measured and investigated. The equivalent birefringence values of nano-rod and nano-zigzag arrays are much larger than crystals found in nature and liquid crystal used in display products. The fact that induced localized plasmon-magnetic field between nanorods dominates the strong phase retardation between p-polarized and s-polarized transmitted wave. For the nano-saw, the strong localized electric field induced between the saw teeth leads to strong SERS signals. Although the bideposited nanoparticles own weak morphological anisotropy, strong optical phase retardation is still detected at wavelengths near 400 nm.