Dmitry A. Bykov

Plasmon-mediated magneto-optical transparency

Magnetic field control of light is among the most intriguing methods for modulation of light intensity and polarization on sub-nanosecond timescales. The implementation in nanostructured hybrid materials provides a remarkable increase of magneto-optical effects. However, so far only the enhancement of already known effects has been demonstrated in such materials. Here we postulate a novel magneto-optical phenomenon that originates solely from suitably designed nanostructured metal-dielectric material, the so-called magneto-plasmonic crystal. In this material, an incident light excites coupled plasmonic oscillations and a waveguide mode. An in-plane magnetic field allows excitation of an orthogonally polarized waveguide mode that modifies optical spectrum of the magneto-plasmonic crystal and increases its transparency. The experimentally achieved light intensity modulation reaches 24%. As the effect can potentially exceed 100%, it may have great importance for applied nanophotonics. Further, the effect allows manipulating and exciting waveguide modes by a magnetic field and light of proper polarization.

Photonic crystals with plasmonic patterns: novel type of the heterostructures for enhanced magneto-optical activity

A multilayer structure consisting of a magnetophotonic crystal with a rare-earth iron garnet microresonator layer and plasmonic grating deposited on it was fabricated and studied in order to combine functionalities of photonic and plasmonic crystals. The plasmonic pattern allows excitation of the hybrid plasmonic-waveguide modes localized in dielectric Bragg mirrors of the magnetophotonic crystal or waveguide modes inside its microresonator layer. These modes give rise to the additional resonances in the optical spectra of the structure and to the enhancement of the magneto-optical effects. The Faraday effect increases by about 50% at the microresonator modes while the transverse magneto-optical Kerr effect demonstrates pronounced peculiarities at both hybrid waveguide modes and microresonator modes and increases by several times with respect to the case of the bare magnetophotonic crystal without the metal grating.

Giant transversal Kerr effect in magneto-plasmonic heterostructures: The scattering-matrix method

The magneto-optical intensity effect (transversal Kerr effect) in a metal-dielectric periodic heterostructure that consists of a metallic grating formed by subwavelength slits and a dielectric substrate magnetized along the slits is shown to be resonantly enhanced by several tens of times in the excitation region of structure eigenmodes—surface plasmon polaritons and Fabry-Perot modes. The Fourier modal and scattering-matrix methods adapted to the case of gyrotropic periodic media have been used. The resonant enhancement of the intensity effect is attributable to the phenomenon of magneto-optical nonreciprocity.

Numerical Methods for Calculating Poles of the Scattering Matrix With Applications in Grating Theory

Waveguide and resonant properties of diffractive structures are often explained through the complex poles of their scattering matrices. Numerical methods for calculating poles of the scattering matrix with applications in grating theory are discussed and analyzed. A new iterative method for computing the scattering matrix poles is proposed. The method takes account of the scattering matrix form in the pole vicinity and relies upon solving matrix equations with use of matrix decompositions. Using the same mathematical approach, we also describe a Cauchy-integral-based method that allows all of the poles in a specified domain to be calculated. Calculation of the modes of a metal-dielectric diffraction grating shows that the iterative method proposed has the high rate of convergence and is numerically stable for large-dimension scattering matrices. An important advantage of the proposed method is that it usually converges to the nearest pole.

Spatial differentiation of optical beams using phase-shifted Bragg grating

We present a theoretical study of a new application of the phase-shifted Bragg grating (PSBG) as an optical spatial differentiator operating in reflection. We demonstrate that the PSBG allows to calculate the first-order spatial derivative at oblique incidence and the second-order derivative at normal incidence. As an example, the differentiator is numerically shown to be able to convert an input 2D Gaussian beam into a 2D Hermite-Gaussian mode. We expect the proposed application to be useful for all-optical data processing.

Temporal differentiation of optical signals using resonant gratings

We study theoretically the possibility of performing temporal differentiation of optical signals using a resonant diffraction grating. We demonstrate that the resonant grating allows the calculation of the first-order derivative of an optical signal envelope in the vicinity of waveguide resonant frequencies in the zeroth transmitted diffraction order. The grating is shown to allow the calculation of the fractional derivative of order 1/2 in the vicinity of Rayleigh-Wood anomalies. Numerical simulations based on the rigorous coupled-wave analysis of Maxwells equations demonstrate the high-quality differentiation of optical signals with temporal features in the picosecond range.

Giant magneto-optical orientational effect in plasmonic heterostructures

Magneto-optical (MO) properties of perforated heterostructures consisting of a thin metallic film perforated with a periodic array of subwavelength slits and a smooth magnetic dielectric are investigated. Rigorous modeling revealed a magnetization-even MO effect determined by the relative change in the intensity of the transmitted or reflected light when the sample is magnetized in-plane perpendicularly to the slits. The effect takes its maximum value when the p-polarized incident light excites quasi-waveguided eigenmodes in the magnetic layer with the phase velocity close to the one of the TE mode in the nongyrotropic planar waveguide.

Extraordinary magneto-optical effect of a change in the phase of diffraction orders in dielectric diffraction gratings

A phase magneto-optical effect in periodic diffraction structures, i.e., a resonant change in the phase of the diffraction order under a change in the magnetization of the material of a structure, has been considered. The theoretical description of the effect is given in terms of the resonant excitation of an eigen-mode of the periodic structure and the magnetization dependence of the frequency of the mode. It has been shown that a wide range of variation of the phase of the zeroth diffraction order is reached at a certain relation between the resonance and nonresonance diffraction processes. The magneto-optical effects in a dielectric diffraction grating formed by a periodic system of slits on a homogeneous substrate have been numerically simulated. The grating is magnetized in the plane and the magnetization vector is perpendicular to the slits of the grating. According to the numerical simulation, the phase magneto-optical effect in the zeroth diffraction order is two orders of magnitude larger than a similar effect for a homogeneous magnetic layer. The numerical simulation of phase magneto-optical effects confirms the theoretical description of the magneto-optical effect.

Diffraction gratings for generating varying-period interference patterns of surface plasmons

The generation of surface plasmon interference patterns using a dielectric diffraction grating with a metal film applied in the substrate region is studied. It is shown by way of numerical simulation within the rigorous electromagnetic theory that high contrast interference patterns with a period several times smaller than that of the diffraction grating can be produced. At the interference maxima, the field intensity is ten times that of the incident wave. Techniques to control the interference pattern period by varying the wavelength and the incidence angle are discussed.

Optical computation of the Laplace operator using phase-shifted Bragg grating

Diffraction of a 3D optical beam on a multilayer phase-shifted Bragg grating (PSBG) is considered. It is shown that the PSBG enables optical computation of the spatial Laplace operator of the electromagnetic field components of the incident beam. The computation of the Laplacian is performed in reflection at normal incidence. As a special case, the parameters of the PSBG transforming the incident Gaussian beam into a Laguerre-Gaussian mode of order (1,0) are obtained. Presented numerical results demonstrate high quality of the Laplace operator computation and confirm the possibility of the formation of Laguerre-Gaussian mode. We expect the proposed applications to be useful for all-optical data processing.