A. G. Zhdanov

Surface-plasmon-induced enhancement of magneto-optical Kerr effect in all-nickel subwavelength nanogratings

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.

Normal and system lupus erythematosus red blood cell interactions studied by double trap optical tweezers: direct measurements of aggregation forces.

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.

Detection of plasmon-enhanced luminescence fields from an optically manipulated pair of partially metal covered dielectric spheres

Using optical tweezers combined with luminescence measurements we detected the optical field around two optically trapped silica microspheres partially covered by metal. By monitoring the luminescence of rhodamine 6G we were able to observe an increase of the local field intensity owing to the coupling of the local surface plasmons at the surfaces of two spheres.

Wood's anomaly in two-dimensional plasmon-assisted magnetophotonic crystals

Woods 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. Woods 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.

Femtosecond time-resolved Faraday rotation in thin magnetic films and magnetophotonic crystals

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.

Second optical harmonic generation as a probe for magnetoelectric properties of multiferroic BiFeO3

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.

Magneto-optical response enhancement in 1D and 2D magnetoplasmonic crystals

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.

Self-similarity effects in optical response of fractal photonic quasi-crystals

One-dimensional photonic microstructures with optical thicknesses chosen according to the fractal sequence of the Cantors 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.

Observation of plasmon-induced optical field enhancement near a pair of partially metal covered dielectric spheres manipulated by optical tweezers

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.

Nonlinear magneto-optical effect in multiferroic material bismuth ferrite

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.