I. A. Kolmychek

Tunable ferroelectric photonic crystals based on porous silicon templates infiltrated by sodium nitrite

Ferroelectric photonic band-gap (PBG) structures are fabricated by the infiltration of sodium nitrite into the nanoporous silicon templates composed by the electrochemical etching of n-type silicon. Reversible spectral tuning of the PBG and of the microcavity mode up to 15nm is attained in the temperature interval from 50to165°C due to the temperature changes of the refractive index of sodium nitrite in nanoporous silicon matrix. Optical second-harmonic generation measurements prove the ferroelectric state of the composed nanocomposite PBG structures.

Two‐Photon Luminescence and Second‐Harmonic Generation in Organic Nonlinear Surface Comprised of Self‐Assembled Frustum Shaped Organic Microlasers

An ultrathin nonlinear optical (NLO) organic surface composed of numerous self-assembled frustum-shaped whispering-gallery-mode resonators displays both two-photon luminescence and second-harmonic-generation signals. A super-second-order increase of the NLO intensity with respect to pump power confirms the microlasing action and practical usefulness of the NLO organic surfaces.

Chirality in nonlinear-optical response of planar G-shaped nanostructures

Chirality effects in optical second harmonic generation (SHG) are studied in periodic planar arrays of gold G-shaped nanostructures. We show that G-shaped structures of different handedness demonstrate different SHG efficiency for the left and right circular polarizations, as well as the opposite directions of the SHG polarization plane rotation. The observed effects are interpreted as the appearance of chirality in the SHG response which allows clear distinguishing of two enantiomers.

Experimental Correlation between Nonlinear Optical and Magnetotransport Properties Observed in Au-Co Thin Films

Magnetic materials where at least one dimension is in the nanometer scale typically exhibit different magnetic, magnetotransport, and magnetooptical properties compared to bulk materials. Composite magnetic thin films where the matrix composition, magnetic cluster size, and overall composite film thickness can be experimentally tailored via adequate processing or growth parameters offer a viable nanoscale platform to investigate possible correlations between nonlinear magnetooptical and magnetotransport properties, since both types of properties are sensitive to the local magnetization landscape. It has been shown that the local magnetization contrast affects the nonlinear magnetooptical properties as well as the magnetotransport properties in magnetic-metal/nonmagnetic metal multilayers; thus, nanocomposite films showcase another path to investigate possible correlations between these distinct properties which may prove useful for sensing applications.

Optical Second Harmonic Generation Chiral Spectroscopy

Chiral spectroscopic study: The intensities of second harmonic generation chiral spectroscopy are obtained from the dispersion of the nonlinear optical susceptibility components, as a function of wavelength for helicenbisquinone thin films (see figure). A single formalism fits all the data simultaneously, and the findings constitute an important milestone towards the development of a new experimental technique.

Coherent and incoherent second harmonic generation in planar G-shaped nanostructures

Azimuthal anisotropy of Stokes parameters of the second harmonic generation (SHG) generated and observed in reflection from a periodic planar area of G-shaped gold nanostructures is studied. A strong anisotropy of both coherent and incoherent SHG components is observed. Finite-difference time-domain calculations prove that the observed effects are due to the anisotropic enhancement of the fundamental radiation within the G-shaped structures.

Plasmon-assisted enhancement of third-order nonlinear optical effects in core (shell) nanoparticles

We study resonant self-action effects of light in plasmonic γ-Fe2O3 (Au) core (shell) nanoparticles (NPs) in a polymer matrix by the spectroscopic Z-scan technique. Plasmon-assisted enhancement of the local optical field in NPs results in the appearance of saturable absorption, as well as in the amplification of nonlinear refraction by more than an order of magnitude compared with nonresonant conditions.

Plasmonic and magnetic effects accompanying optical second-harmonic generation in Au/Co/Au nanodisks

Optical second-harmonic (SH) generation in Au/Co/Au sandwich-like nanodisks is studied, using several experimental techniques, at SH frequency being close to that of the plasmon resonance in the system. The dependences of the relative amplitude and phase of the magnetization-induced SH component on the angle of incidence are found to significantly differ from those measured for a continuous Au/Co/Au trilayer film. A phenomenological description of the observed effects is proposed, with special emphasis on resonant excitation of the local plasmon modes by the nonlinear sources induced in the nanodisks.

First and second order in magnetization effects in optical second-harmonic generation from a trilayer magnetic structure

Linear and nonlinear optical properties of a thin planar CoFe/Al2O3/CoFe structure for different angles of incidence of the fundamental radiation are studied by means of the magneto-optical Kerr effect and magnetization-induced second-harmonic generation (SHG). The composition of this multilayered structure supports the appearance of the antiferromagnetic state, which leads to nonreciprocal optical effects and is discussed in terms of the magnetic toroid moment. We show that in accordance with the phenomenological description, SHG magnetic hysteresis loops for a linearly polarized pump beam are determined by linear in magnetization M components of the SHG polarization, while for a circularly polarized pump such a description necessarily involves both linear and quadratic in M components of the nonlinear polarization. Symmetry analysis of the magnetization-induced SHG supports the differences between the cases of linear and circular polarization of the incident radiation observed in the experiment, as well as a partial suppression of first in magnetization SHG contributions. Relative values of the linear and quadratic in magnetization components of the SHG polarization are estimated for the trilayer structure and for a reference homogeneous ferromagnetic film.

Second Harmonic Generation in Core (Shell) γ-Fe2O3 (Au) Nanoparticles

The films containing core (shell) γ-Fe2O3 (Au) nanoparticles that possess the plasmon resonance at the wavelength 550 nm are prepared. The second harmonic generation in these structures is shown to be diffuse and depolarized, that is typical for the hyper-Rayleigh scattering.. The studies of the magnetization-induced second harmonic generation shows that the ratio of the magnetic to nonmagnetic components of the hyperpolarizability of a single nanoparticle, γM/γ0 ~ 0.4 in the field of about 3 kOe.