In order to enable optical systems to operate with a high degree of compactness and reliability it is necessary to combine large number of optical functions in small monolithic structures. A development, somewhat reminiscent of that that took place in Integrated Electronics, is now beginning to take place in optics. The initial challenge in this emerging field, known appropriately as "Integrated Optics", is to demonstrate the possibility of performing basic optical functions such as light generation, coupling, modulation, and guiding in Integrated Optical configurations. The talk will review the main theoretical and experimental developments to date in Integrated Optics. Specific topics to be discussed include: Material considerations, guiding mechanisms, modulation, coupling and mode losses. The fabrication and applications of periodic thin film structures will be discussed.

Integrated optics

A leather matrix (LM) was used as a microwave-absorptive substrate to surface coat with Cu@Ag nanoflakes to prepare a lightweight, high-performance and wearable nanocomposite shielding material. The essence of this strategy is that the shielding capacity of the nanocomposite is dependent not only on the reflectivity of Cu@Ag nanoflakes to microwaves, but also on the absorption capacity of the LM to the incident microwaves via dielectric loss. In this way, an extremely low content of Cu@Ag nanoflakes is enough for LM-Cu@Ag to achieve superior high shielding ability (∼100 dB), thus showing lightweight high-performance shielding ability (specific shielding effectiveness up to 120 dB cm3 g−1) in a board frequency range (10–3000 MHz, 8–12 GHz). Moreover, this nanocomposite shielding material is also able to be tailored into wearable clothing, demonstrating its practical wearability.

Lightweight and high-performance electromagnetic radiation shielding composites based on a surface coating of Cu@Ag nanoflakes on a leather matrix

We present a theoretical study of the dispersion and energy properties of the eigenwaves (TE- and TM-modes) in a four-layer structure composed of a magneto-optical yttrium iron garnet guiding layer on a dielectric substrate covered by a planar nanocomposite guiding multilayer. The bigyrotropic properties of yttrium-iron garnet are taken into account for obtaining the dispersion equation and an original algorithm for the guided modes identification is proposed. We demonstrated the polarization switching of TE- and TM-modes dependent on the geometrical parameters of the guiding layers. The dispersion diagrams and field profiles are used to illustrate the change of propagation properties with variation of the multilayer thickness ratio of the nanocomposite's layers. The energy flux distributions across the structure are calculated and the conditions of the optimal guiding regime are obtained. The power switching ratio in the waveguide layers of about 6 dB for the wavelength range of 100 nm is shown to be achieved.

https://iopscience.iop.org/article/10.1088/0022-3727/49/43/435103/pdf

Four-layer nanocomposite structure as an effective optical waveguide switcher for near-IR regime

Probing the hybridized magnetic interface between organic semiconductor (OSC) and ferromagnetic (FM) layers has drawn significant attention in recent years because of their potential in spintronic applications. Recent studies demonstrate various aspects of organic spintronics such as magnetoresistance, induced interface moment etc. However, not much work has been performed to investigate the implications of such OSC/FM interfaces on the magnetization reversal and domain structure which are the utmost requirements for any applications. Here, we show that non-magnetic Fullerene can obtain non-negligible magnetic moment at the interface of Fe(15 nm)/C60(40 nm) bilayer. This leads to substantial effect on both the magnetic domain structure as well as the magnetization reversal when compared to a single layer of Fe(15 nm). This is corroborated by the polarized neutron reflectivity (PNR) data which indicates presence of hybridization at the interface by the reduction of magnetic moment in Fe. Afterwards, upto 1.9 nm of C60 near the interface exhibits magnetic moment. From the PNR measurements it was found that the magnetic C60 layer prefers to be aligned anti-parallel with the Fe layer at the remanant state. The later observation has been confirmed by domain imaging via magneto-optic Kerr microscopy.

/pdf/effect-of-magnetic-fullerene-on-magnetization-reversal-4kg36zlz46.pdf

Effect of magnetic fullerene on magnetization reversal created at the Fe/C60 interface.

The forces, deformations, and stresses generated in macromolecules attached to single-domain magnetic nanoparticles under the influence of a low-frequency (nonheating) magnetic field have been analyzed analytically and numerically. It has been shown that, in bioactive macromolecules, an alternating magnetic field with an induction of 0.1–1.0 T and a circular frequency of ≲104 s−1 can induce forces up to several hundred piconewtons, absolute deformations up to a few tens of nanometers, as well as compressive and shear stresses exceeding 107 Pa. These mechanical stimuli are sufficient for a significant change of interatomic distances in active centers, conformation of macromolecules, and even a breaking of some bonds, which makes it possible to develop a new technological platform for targeted delivery of drugs, remote control of their activity, and cancer-cell destruction.

Single-domain magnetic nanoparticles in an alternating magnetic field as mediators of local deformation of the surrounding macromolecules

This article investigates the equilibrium states of square-planar arrays of magnetic dipoles. It has been demonstrated that in the presence of an exchange interaction the main equilibrium states are the configurations of dipoles oriented along the system diagonal, along its side, as well as configurations with vortex structures, which may differ by location of the vortex center and, respectively, by magnitude and direction of the magnetic moment of the system. Also the conditions for transitions in the equilibrium configurations, when influenced by a plane field affecting the whole array, or by a normal local field affecting a part of the system dipoles, were considered. The possibility to control magnetic moment of the dipoles system through transitions between different vortex configurations, including a configuration with zero total magnetic moment, has been shown.

Equilibrium state of planar arrays of magnetic dipoles in the presence of exchange interaction

The nonlinear dynamic modes of a chain of coupled spherical bodies having dipole magnetic moments that are excited by a homogeneous ac magnetic field are studied using numerical analysis. Bifurcation diagrams are constructed and used to find conditions for the presence of several types of regular, chaotic, and quasi-periodic oscillations. The effect of the coupling of dipoles on the excited dynamics of the system is revealed. The specific features of the Poincare time sections are considered for the cases of synchronous chaos with antiphase synchronization and asynchronous chaos. The spectrum of Lyapunov exponents is calculated for the dynamic modes of an individual dipole.

Regular and chaotic dynamics of a chain of magnetic dipoles with moments of inertia

Vortex equilibrium states of planar square lattices of magnetic dipoles in the presence of the exchange interaction have been studied. It has been shown that the vortex equilibrium configurations differ in the position of the vortex center and, correspondingly, in the magnitude and direction of the total magnetic moment of the system. In the case of the position of the vortex center in the center of the array, the total magnetic moment of the system is zero. The vortex center moves in the direction perpendicular to the field under the action of the external planar magnetic field on the system. Thus, the transitions between different equilibrium vortex configurations are implemented and the magnetic moment of the system of dipoles is controlled.

Vortex structures in planar lattices of magnetic dipoles in the presence of exchange coupling

Phase transitions in hexagonal lattices with three and four rows of dipoles arising as a result of the reorientation of different sets of dipoles by the external field have been studied. The conditions of the implementation of two types of symmetric phase transitions and the asymmetric transitions, when the configurations of the system to the left and to the right of the excitation region are different, have been established. Merging of two regions of the phase transitions has been considered. Unidirectional phase transitions, in which either the left or the right phase transition front propagates from the excitation region along the lattice, have been obtained in a lattice with four rows of dipoles. The variations of the total dipole moment of the system and the energy of the dipole-dipole interaction during the phase transitions have been given.

Excitation of phase transitions in dipole lattices

Dipole lattices, which represent square dipole arrays, are investigated. Various types of equilibrium configurations of arrays are obtained, and conditions are shown under which these configurations are established. On the basis of parametric bifurcation diagrams, the main types of regular and chaotic oscillation regimes of the total dipole moment of a system are considered and their dependence on the amplitude, frequency, and polarization of an alternating field, as well as on the initial equilibrium configuration of arrays, is analyzed. Scenarios of the onset of chaotic regimes are demonstrated, including those that occur via the establishment and variation of quasiperiodic oscillations of the dipole moment of a system. The dynamic bistability state is revealed in which a stochastic resonance—an increase in the response of a system to a harmonic signal in the presence of noise—can be implemented.

A. M. Shutyi

Papers

Equilibrium state of planar arrays of magnetic dipoles in the presence of exchange interaction

Regular and chaotic dynamics of a chain of magnetic dipoles with moments of inertia

Vortex structures in planar lattices of magnetic dipoles in the presence of exchange coupling

Excitation of phase transitions in dipole lattices

Regular and chaotic dynamics of the dipole moment of square dipole arrays