Femtosecond time-resolved Faraday rotation is studied in magnetic garnet films and magnetophotonic crystals. Femtosecond dynamics of Faraday angle governed by multiple reflection interference and Faraday effect non-reciprocity is revealed by using polarization-sensitive ultrafast correlation technique.

Direct measurements of aggregation forces in piconewton range between two red blood cells in pair rouleau are performed under physiological conditions using double trap optical tweezers. Aggregation and disaggregation properties of healthy and pathologic (system lupus erythematosis) blood samples are analyzed. Strong difference in aggregation speed and behavior is revealed using the offered method which is proposed to be a promising tool for SLE monitoring at single cell level.

Double optical tweezers is suggested for studying red blood cell aggregation. Quantitative measurements of interaction forces between a pair of RBC are performed. Comparative analysis of aggregation for healthy and pathological blood samples is shown.

Enhancement of transversal magneto-optical Kerr effect (TKE) is controlled experimentally in magnetoplasmonic subwavelength nanogratings made of nickel films by resonant excitation of surface plasmon-polaritons (SPPs). Almost one order of magnitude increase of the TKE value is observed in the spectral range of Wood’s anomaly corresponding to the fulfillment of the phase-matching conditions for SPP excitation.

Aggregation peculiarities of red blood cells (RBCs) in autologous plasma are studied using double trap optical tweezers technique. The positions of RBCs are controlled with submicrometer accuracy by two optical traps formed by strongly focused laser beams (lambda = 1064 nm). Quantitative measurements of interaction forces between RBCs in pair aggregates are performed. Depending on the RBCs aggregation force, four different end-points of disaggregation induced by optical trap movement are revealed. Analysis of experimental force dependence on the distance between two RBCs during disaggregation is in a good agreement with the model of ring-shaped interaction surfaces of RBCs in pair aggregate. Aggregation velocities measured are shown to be strongly different for healthy and pathologic (System Lupus Erythematosis - SLE) blood samples.

Optical tweezers technique combined with local confocal luminescence spectroscopy is suggested as a tool for investigation of local optical fields. Utilizing this method plasmon-enhanced optical fields inside a pair of dielectric 2 μm spheres partially covered by 70 nm silver nanoparticles are visualized via field enhanced luminescence of rhodamine dye solution. Positions of the particles are controlled with submicrometer accuracy by two optical traps formed by strongly focused laser beams with λ=980nm. A supplementary beam from CW laser with λ=532nm provided for luminescence excitation is also focused into the sample cavity just to the trapping area. In order to obtain spatial filtering of the signal and separate luminescence signal from an area near the spheres pin-hole based confocal system is designed. The focal volume available for luminescence signal collection turns out to be approximately 3μm x 3 μm x 5 μm. Since optical field is enhanced in the region near plasmon-active 2 μm spheres the enhancement of luminescence intensity is observed. Collective plasmonic effects in two-particle measurements are also considered.

The results of experimental observation of magneto-optical Kerr effect (MOKE) enhancement caused by surface plasmon-polaritons (SPP) excitation in 1D and 2D magnetoplasmonic crystals are presented. One-dimensional nickel magnetoplasmonic crystals have periodic structure formed by periodic nickel grooves made on nickel surface. The period of the structure is 320 nm and the depth of the grooves is 50 nm. The second group of the samples represents itself a 2D self-assembled hexagonally ordered monolayer of polystyrene (PS) microspheres with diameters from 500 to 760 nm and covered by 100- nm - thick nickel film. MOKE measurements performed in transversal configuration demonstrate that SPP excitation lead to transversal Kerr effect (TKE) enhancement resulting as a sharp peak in TKE spectrum.

The magneto-optical Faraday effect is studied in one-dimensional magnetophotonic crystals (MPCs). Mechanisms of a strong enhancement of the Faraday rotation at the edges of the photonic band gap are considered. High difference of refractive indexes of bismuth-substituted yttrium iron garnet (Bi:YIG) and SiO2 layers provides a strong spatial localization of the optical field in Bi:YIG layers, which leads to manifold Faraday rotation enhancement at the photonic band edges. The Faraday rotation angle in the finite MPCs appears to be a nonlinear function of the total thickness of magnetic material in the stack that can be interpreted as the nonlinear Verdet law. Relation between the enhancement of the Faraday rotation and localization of optical field in magnetic layers is treated as a Borrmann-type effect. This relation shows that the Faraday rotation can be considered as a measure of the density of photonic states trapped within Bi:YIG layers.

Wood's anomaly is experimentally observed in 2D plasmon-assisted nickel magnetophotonic crystals. It is shown to be accompanied by ≃ 2 times enhancement of longitudinal Kerr effect. Wood's anomaly appears only for p-polarization of incident light at any angle of incidence in the range between 10° and 70°. It vividly indicates surface plasmon-polariton inducing on nickel surface. The experimental results are proved by numerical calculations.

Magneto-optical Kerr effect in 2D magnetophotonic crystals (slabs) formed from the array of nickel nanorods is considered. The peculiarities of optical properties have magneto-plasmonic nature. The experimental results are proved by numerical calculations.

One-dimensional photonic microstructures with optical thicknesses chosen according to the fractal sequence of the Cantor's ladder are considered. Experimental samples made by electrochemical etching of porous silicon are studied. Both numerical calculations and experimental results demonstrate self-similarity in reflection spectrum. Numerical calculations demonstrate self-similarity in space distribution and time-resolved response caused by self-similarity in morphology.

Based on the theoretical symmetry analysis of the nonlinear electric susceptibility, second harmonic generation is examined as a probe for detection of various type of ordering: magnetic, ferroelectric, ferroelastic. The nonlinear optical response of multiferroics is illustrated by the example of bismuth ferrite BiFeO3. It is shown that magnetically induced second harmonic response as well as anisotropic part of ferroelectrically induced second harmonic depends on mechanical (ferroelastic) ordering. This is one of the aspects of order parameters coupling in multiferroics.

Spectral dependences of Faraday rotation angle in one-dimensional garnet-based magnetophotonic crystals are considered. The enhancement of Faraday angle is demonstrated at the photonic band gap (PBG) edge both theoretically and experimentally. It is shown to be associated with the optical field localization in the magnetic layers of the structure. The advantages of magnetophotonic crystals in comparison with traditional magnetic microcavities are discussed. The specially designed microcavity structures optimized for the Faraday effect enhancement at the PBG edge are suggested.

Characteristic features of magnetic field-induced phase transitions incommensurate–commensurate (IC–C) phase in multiferroics are considered. An example of such substances is the ferroelectromagnet bismuth ferrite BiFeO3. It was shown that the interaction between electric and magnetic subsystems can result in electric field induced shift of critical value for the magnetic field, at which the phase transition from spatially modulated to the homogenous antiferromagnetic state takes place. This change has value 0.5 T in the electric field 50 kV/cm. Phase diagrams in the magnetic field–electric field coordinates are plotted.

The specific features of the “incommensurate-commensurate” phase transitions induced by a magnetic field in multiferroics (materials with coexisting magnetic and electric ordering) are considered. These materials are ferroelectromagnets, for example, bismuth ferrite BiFeO3 and BiFeO3-based compounds, which have spatially modulated spin structures. It is shown that the interaction between the electric and magnetic subsystems of the multiferroic material can lead to an electric-field-induced shift of the critical magnetic field corresponding to the transition from a spatially modulated state to a homogeneous antiferromagnetic state. According to the theoretical estimates obtained for material parameters characteristic of the bismuth ferrite, this shift is of the order of 0.5 T in an electric field of 50 kV/cm. The phase diagrams are constructed in the “electric field-magnetic field” coordinates. The results of calculations performed in the harmonic incommensurate structure approximation are compared with the exact soliton solution.

Based on the group theoretical analysis of the nonlinear electric susceptibility second harmonic response in different magnetic states of multiferroic bismuth ferrite is considered. It is shown that nonlinear magneto-optic effect can serve as an effective tool for spin cycloid structure detection in bulk material and probing homogenous antiferromagnetic state in thin films of bismuth ferrite. The study of antiferromagnetic state that determines magnetoelectric properties of the material is important in the context of practical applications in microelectronic and magnetic storage.