Irina A. Kolmychek

Organic microstructures provide unique possibilities for micro-flexible photonics, giving birth to bright photoluminescent waveguides and resonators. To a large extent, the functionality of such structures is governed by their crystalline structure, which is quite difficult to study at the microscale. At the same time, optical microscopy techniques can give access to structural analysis of microstructures. Here we demonstrate that linear and nonlinear optical probes reveal birefringence and polarization effects within single microstructures such as microrod and microring. The observed nonlinear optical anisotropy confirms the preservation of local crystalline structure within HDBP microrings, similar to those of regular right-angled-shape crystals, which strongly modulates the spectra of whispering gallery modes in HDBP ring resonators.

Recent studies of optical, magneto-optical, and nonlinear optical effects in epitaxial iron garnet films and arrays of ferromagnetic metal nanoparticles on their surface have been reviewed. It has been shown that second and third-harmonic generation microscopy makes it possible to visualize the surface domain structure of garnet. The role of metasurfaces in the formation of the quadratic nonlinear optical response of the composite structure at the micro- and macroscales has been analyzed. The possibility of pinning of domain walls in garnet by metal ferromagnetic metasurfaces deposited over it, as well as the optical visualization of such pinning by means of polarization microscopy and analyzing the diffraction of laser radiation on domains, has been demonstrated.

Magneto-plasmonic structures have been a subject of tremendous attention of researchers in recent decades as they provide unique approaches regarding the efficient control of optical, magneto-optical, and nonlinear-optical effects. Among others, magneto-plasmonic crystals (MPCs) have become one of the most studied structures, known for their high-quality tunable resonant optical properties. Here, we present the results of experimental and numerical studies on the functional magneto-optical (MO) response of planar 1D plasmonic crystals composed of Co/Au stripes of submicron period on the surface of a 3 μm thick rare-earth garnet layer. The experimental and numerical studies confirm that the wavelength–angular spectra of such structures contain a set of tunable resonant features in their optical and magneto-optical response, associated with the excitation of (i) surface plasmon polaritons at the Co/Au grating–garnet interface, as well as (ii) waveguide (WG) modes propagating in the garnet slab. A comparison of the MO effects in the transversal and longitudinal magnetization of the plasmonic structures is presented. We show that the most efficient Fano-type MPC magneto-optical response is realized for the WG modes of the first order for the longitudinal magnetization of the structure. Further perspectives regarding the optimization of this type of plasmonic crystal are discussed.

Control over the magnetic domain structure of garnet films is an important task that is attractive for a wide range of applications. One of the possible approaches here is based on the introduction of additional structured magnetic coverages interacting with the garnet layer. In this study, we demonstrate that arrays of asymmetric ferromagnetic cobalt particles regularly arranged on the surface of Lu,Bi-substituted iron garnet film influence the orientation and width of the stripe domains, as stems from the optical microscopy, magneto-optical and diffraction studies. We also show that triangular-shaped Co particles induce the asymmetry of the magnetic field dependence on the magneto-optical Kerr effect of the composite structure. We assert that the key effect here is the interaction of the residual magnetic moments of Co particles with the surface closure domains.

The interaction of laser radiation with magnetic media is a rapidly developing field of research, offering broad possibilities both for observing new effec

Composite magnetic nanostructures are a subject of high research interest, as they provide a number of exciting effects absent in live nature. Among others, much attention has been paid to the studies of exchange coupling in antiferromagnetic/ferromagnetic (AFM/FM) films, which leads to the pinning effect. It manifests itself as a widening and shift of the magnetic hysteresis loop with respect to zero value of the external magnetic field oriented along the pinning direction. In this work, we report on comparative studies of linear and nonlinear magneto-optical effects under the laser-induced switching of the pinning effect in IrMn/CoFe films of various thickness of the ferromagnetic CoFe layer. We found that the magneto-optical response of the pinned AFM/FM nanofilms appears with different hysteresis loop parameters in the transverse magneto-optical Kerr effect (MOKE) and interface-sensitive magnetization-induced second harmonic generation (SHG), indicating the diversity of the magnetic effects at interfaces compared to the bulk of the films.

Arrays of metal nanostructures have attracted much interest due to their unique potential as optical nanoantennas and nanosensors. Here we use the second harmonic generation (SHG) microscopy technique for the studies of the nonlinear optical (NLO) response of cobalt nanoparticles of triangular and trapezoid shapes separated from a Py/Si₃N₄ film by a 1.5 nm thick MgO spacer. We demonstrate that the nonsymmetric elongated shape of planar nanoparticles along with the strong light localization effects result in the enhancement of the NLO response, including SHG and two-photon fluorescence. We also demonstrate that the efficiency of the SHG in nanoparticles is rather sensitive to the polarization of the incident laser beam, the visibility of the nanostructures in the nonlinear microscopy images being the highest for the linear polarization of the laser beam.

Intensive studies of hyperbolic metamaterials (HMMs) are induced by unique optical properties of this type of artificial media associated with their hyperbolic dispersion. Special attention is attracted to the nonlinear optical response of HMMs, which reveals anomalous behavior in definite spectral regions. Third-order nonlinear optical self-action effects that are perspective for applications were analyzed numerically, whereas such experiments have not been performed up to now. In this work we study experimentally the effects of the nonlinear absorption and refraction in ordered arrays of gold nanorods in porous aluminum oxide. We demonstrate strong enhancement and sign reversal of these effects in the vicinity of the epsilon-near-zero spectral point due to the resonant light localization and transition from elliptical to hyperbolic dispersion regimes.