V. A. Kotov

Magnetic photonic crystals: 1-D optimization and applications for the integrated optics devices

The optimization of multilayer one-dimensional (1-D) magnetophotonic crystals (MPCs) with multiple phase shifts, enabling their design to be tailored to practical photonics applications, is reported. The properties of sample optimized structures suitable for application in infrared intensity modulators are discussed. A novel scheme of high-resolution magnetic field sensing using MPCs is proposed. The effect of material absorption on spectral properties is shown.

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.

Annealing behaviour and crystal structure of RF-sputtered Bi-substituted dysprosium iron-garnet films having excess co-sputtered Bi-oxide content

We investigate the magneto-optic properties, crystal structure and annealing behaviour of nano-composite media with record-high magneto-optic quality exceeding the levels reported so far in sputtered iron-garnet films. Bi-substituted dysprosium–gallium iron-garnet films having excess bismuth oxide content are deposited using RF co-sputtering, and a range of garnet materials are crystallized using conventional oven-annealing processes. We report, for the first time ever, the results of optimization of thermal processing regimes for various high-performance magneto-optic iron-garnet compositions synthesized and describe the evolution of the optical and magneto-optical properties of garnet-Bi-oxide composite-material films occurring during the annealing processes. The crystallization temperature boundaries of the system (BiDy)3(FeGa)5O12 : Bi2O3 are presented. We also report the results of x-ray diffraction and energy-dispersive x-ray spectroscopy studies of this recently developed class of high-performance magneto-optic composites. Our hypothesis of iron oxides being the cause of excess optical absorption in sputtered Bi-iron-garnet films is confirmed experimentally.

Effect of oblique light incidence on magnetooptical properties of one-dimensional photonic crystals

We have investigated the magnetooptical properties of one-dimensional magnetic photonic crystals for the case of oblique light incidence. We developed a theoretical model based on the transfer matrix approach. We found several new effects such as transmittance resonance peak shift versus external magnetic field and the Faraday effect dependence on the incidence angle. We discuss several possible one-dimensional magnetic photonic crystals applications for the optical devices.

Hybrid structures of magnetic semiconductors and plasmonic crystals: a novel concept for magneto-optical devices [Invited]

We propose here to combine magnetic semiconductors and plasmonic crystals to obtain a new class of devices, in which magneto-optical effects are dramatically enhanced. So far we have studied the two building blocks separately, and we demonstrate here features of these systems that make them appealing for combination. Namely, for magnetic semiconductors we demonstrate efficient tools for manipulating their magnetization. In particular, we show that in paramagnetic (Ga,Mn)As the magnetic ions can be oriented optically. For ferromagnetic (Ga,Mn)As an ultrafast strain pulse moves the magnetization out of its equilibrium position, inducing a subsequent precessional motion about the equilibrium orientation. For plasmonic crystals, on the other hand, we show that the magneto-optical effects are dramatically enhanced in both reflection and transmission. From combining the two systems, we expect to be able to obtain magneto-optical materials that can be controlled efficiently through manipulation of the magnetization of the magnetic semiconductor onto which the plasmonic crystal is deposited.

New magnetooptical materials on a nanoscale

In this review new nanostructured materials for magnetooptics are discussed: magnetic photonic crystals and magnetic perforated metal/dielectric films. It is shown that under some conditions the magnetooptical effects in such structures can be significantly enhanced remaining the optical transmittance on a relatively high level. This effect is primarily due to the proper structuring of the material on a nanoscale. Special attention is paid to magnetic substances which are most appropriate for modern magnetooptics.

Faraday effect enhancement in metal-dielectric plasmonic systems

Magnetooptical effects in the metal/dielectric heterostructure, consisting of a thin metallic layer with the array of parallel subwavelength slits and a uniform dielectric layer magnetized perpendicular to its plane, are investigated. Calculations, based on the rigorous coupled-wave analysis of Maxwells equations, demonstrate that in such structures the Faraday and Kerr rotation can be significantly enhanced in the near infrared optical range. It is possible by varying thickness of the magnetic film to make Faraday rotation and transmittance peaks coincident and achieve the increase in the Faraday effect by more than an order of magnitude at the transmittance of 40-45%. It is shown that the excitation of the surface plasmon polaritons and quasi-guided TM- and TE- modes in the dielectric layer mostly governs the enhancement of the Faraday rotation.

Magnetic heterostructures with low coercivity for high-performance magneto-optic devices

In this work, we analyse the method of forming magneto-optically active heterostructures based on magnetic layers with different magnetic properties. Layers of one type possess a high effective constant of uniaxial magnetic anisotropy K ∗ u for which the condition K ∗ u = Ku − 2πM 2 s > 0 is fulfilled, where Ku is the constant of uniaxial magnetic anisotropy and 2πM 2 s is the demagnetizing energy, and layers of the second type used possess in-plane or quasi-in-plane magnetization, in which the condition K ∗ u = Ku − 2πM 2 s < 0 holds true. The layers of the first type, which we refer to as layers of positive effective uniaxial magnetic anisotropy, may have the composition Bi2Dy1Fe4Ga1O12 and the layers of second type the composition Bi3Fe5O12, which may have very high magneto-optic (MO) figure of merit and are therefore very attractive for the development of MO transparencies and ultra-fast switches. We discuss the optimization of triple-layer structure parameters aimed at achieving a high MO figure of merit simultaneously with low coercivity and high remanent magnetization and possessing rectangular hysteresis loops. The results of the experimental study of the MO properties achieved in garnet heterostructures fabricated using RF sputtering are also described. We show that the proposed paradigm of using new magnetic material combinations demonstrating significantly improved magnetic and MO properties may be realized when working with heterostructures based on Bi-substituted ferrite garnets grown on (1 1 1)-oriented garnet substrates. (Some figures may appear in colour only in the online journal)

Intensity magnetooptical effect in magnetoplasmonic crystals

Significant increase of the intensity magnetooptical effect (transversal Kerr effect) is observed in transmission for a magnetoplasmonic crystal consisting of the perforated noble-metal film attached to a smooth magnetic dielectric layer. It is largely due to the magnetic field induced shift of the Fano resonances in transmission associated with the surface plasmon polaritons excited at the metal/magnetic-dielectric interface. It is shown that the quasi-guided modes of the magnetic layer also lead to the enhancement of the intensity magnetooptical effect. The considered magnetoplasmonic structures are of great importance for applications in telecommunication and molecular sensing as they also drastically enhance other magnetooptical effects.

Refraction of s- and p-polarized electromagnetic waves at the interface between a nonmagnetic insulator and an easy-axis centroantisymmetric antiferromagnet

Using the example of an easy-axis antiferromagnet with a magnetic structure of 4z−2x+I− the effect of antisymmetric magnetoelectric interaction on the nature of the refraction of the bulk s- or p-polarized electromagnetic waves, incident from outside at any angle to the surface of the magnet, is studied analytically. The easy magnetic axis is collinear to the normal to the medium interface.