Oleg A. Aktsipetrov

Bio: Oleg A. Aktsipetrov is an academic researcher from Moscow State University. The author has contributed to research in topics: Second-harmonic generation & Photonic crystal. The author has an hindex of 31, co-authored 241 publications receiving 3457 citations. Previous affiliations of Oleg A. Aktsipetrov include Brookhaven College & Russian Academy of Sciences.

Ultrafast Transport of Laser-Excited Spin-Polarized Carriers in Au/Fe/MgO(001)

Abstract: Hot carrier-induced spin dynamics is analyzed in epitaxial Au=Fe=MgOð001Þ by a time domain approach. We excite a spin current pulse in Fe by 35 fs laser pulses. The transient spin polarization, which is probed at the Au surface by optical second harmonic generation, changes its sign after a few hundred femtoseconds. This is explained by a competition of ballistic and diffusive propagation considering energy-dependent hot carrier relaxation rates. In addition, we observe the decay of the spin polarization within 1 ps, which is associated with the hot carrier spin relaxation time in Au.

Asymmetric Optical Second-Harmonic Generation from Chiral G -Shaped Gold Nanostructures

Abstract: We present a new electromagnetic phenomenon—the asymmetric second-harmonic generation from planar chiral structures. The effect consists in distinguishing the handedness of a chiral material by rotating the sample in an experiment involving solely linearly polarized light. This phenomenon originates in the surface plasmon resonance of chiral gold nanostructures, where homodyne interference of anisotropic and chiral electric and/or magnetic multipoles appears to play an important role. The remarkable expansion of nanoscience and nanotechnology during the past decade has led to strong interest in the investigation of nanoscale optical fields and the development of tools for their study. Consequently, the optical properties of metallic nanostructures are of great current significance from both fundamental and practical points of view [1]. One of the most important effects in light scattering by these nanostructures is the enhancement, up to several orders of magnitude, of the field intensity, which occurs in a confined nanoscale region around the particles. This enhancement originates from a combination of the electrostatic lightning-rod effect, due to the geometric singularity of sharp curvatures, and localized surface plasmon resonances. The latter are a consequence of the metal nanoparticle’s ability to build up structural resonances of the collective oscillations of the metal electron plasma. The resonances depend on the particle’s geometry and dielectric properties, as well as on the refractive index of its surroundings. Second-harmonic generation (SHG) is known to be surface and interface sensitive on the atomic scale. Therefore, its application to the study of the nonlinear optical response of metal nanostructures, with their pronounced optical resonances and high surface-to-volume ratio, is particularly suitable for improving the insight into the relationship between optical properties and morphology at the nanoscale. Symmetry issues are closely related to the polarization dependence of the nonlinear optical responses since, within the electric dipole approximation, SHG is forbidden in materials with inversion symmetry. Planar nanostructures are particularly interesting because, using modern lithography techniques, dielectric and metallic forms of complicated geometry can be created, including planar chiral designs [2,3]. The types of structures have recently

Magnetophotonic crystals

Abstract: In much the same way that semiconductor crystals affect the propagation of electrons, photonic crystals (periodic composites of macroscopic dielectric media of different refractive index) affect the propagation of light, providing a new mechanism to control and manipulate the flow of light. When the constitutive material of PCs is magnetic, or even only a defect introduced into the periodic structure is magnetic, the resultant PCs (let us simply refer to as magnetophotonic crystals (MPCs) hereafter) exhibit unique optical and magneto-optical responses: The strong photon confinement associated with the magnetic defect can be exploited to enhance and optimize magneto-optical (MO) effects and optical non-linearity of existing materials.

Plasmons reveal the direction of magnetization in nickel nanostructures.

Abstract: We have applied the surface-sensitive nonlinear optical technique of magnetization-induced second harmonic generation (MSHG) to plasmonic, magnetic nanostructures made of Ni. We show that surface plasmon contributions to the MSHG signal can reveal the direction of the magnetization. Both the plasmonic and the magnetic nonlinear optical responses can be tuned; our results indicate novel ways to combine nanophotonics, nanoelectronics, and nanomagnetics and suggest the possibility for large magneto-chiral effects in metamaterials.

Multiferroic and magnetoelectric materials

Abstract: A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements. A ferromagnetic crystal exhibits a stable and switchable magnetization that arises through the quantum mechanical phenomenon of exchange. There are very few 'multiferroic' materials that exhibit both of these properties, but the 'magnetoelectric' coupling of magnetic and electrical properties is a more general and widespread phenomenon. Although work in this area can be traced back to pioneering research in the 1950s and 1960s, there has been a recent resurgence of interest driven by long-term technological aspirations.

Photonic crystals

Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

Photophysical, photochemical and photocatalytic aspects of metal nanoparticles

Abstract: Unique electronic and chemical properties of metal nanoparticles have drawn the attention of chemists, physicists, biologists, and engineers who wish to use them for the development of new generation nanodevices. Metal nanoparticles such as gold and silver show noticeable photoactivity under UV−visible irradiation as is evident from the photoinduced fusion and fragmentation processes. Binding a photoactive molecule (e.g., pyrene) to metal nanoparticle enhances the photochemical activity and renders the organic−inorganic hybrid nanoassemblies suitable for light-harvesting and optoelectronic applications. The nature of charge-transfer interaction of fluorophore with gold surface dictates the pathways with which the excited-state deactivates. Obtaining insight into energy and electron-transfer processes is important to improve the charge separation efficiencies in metal−fluorophore nanoassemblies and photocatalytic activity of metal−semiconductor composites.