Interference of counterpropagating waves in a nonreciprocal chiral medium

It is established that the partial fluxes of counterpropagating waves in a layer of a nonreciprocal chiral medium exhibit exponential decay, while the interference flux is sustained and exhibits oscillations in depth of the layer. The condition of existence of the interference flux in a nonabsorbing medium is formulated.     

Optical nonreciprocal devices with a silicon guiding layer fabricated by wafer bonding

Optical nonreciprocal devices with a silicon guiding layer fabricated by wafer bonding are proposed. The optical nonreciprocal devices are composed of a magneto-optic waveguide with a magnetic garnet/Si/SiO2 structure. Nonreciprocal characteristics are obtained by an evanescent field penetrating into the upper magnetic garnet cladding layer. Several kinds of the optical nonreciprocal device are investigated with the magneto-optic waveguide and designed at a wavelength of 1.55 microm. As a preliminary experiment, wafer bonding between Gd3Ga5O12 and Si was studied. Wafer bonding was successfully achieved with heat treatment at 220 degrees C in H2 ambient.     

Analysis of nonreciprocal mode propagation in magneto-optic rib-waveguide structures with the spectral-index method

Passive linear nonreciprocal devices, such as isolators or circulators, require gyrotropic media. If there is a contribution to the dielectric permittivity tensor of odd order in the magnetization, the modes propagate differently in the forward and the backward directions. We investigate dielectric waveguides that are formed by a rib of rectangular cross section on top of a planar structure. The rib or planar structure may consist of layers, each of which may be gyrotropic. We extend the spectral-index method for calculating differences between forward- and backward-propagation constants. A new design for an efficient nonreciprocal phase shifter is proposed.     

Simple optical profiling of complex guiding structures

Working with complex guiding structures such as holey fibers requires coupling light into the input face of the structure. We use a simple in vivo technique to determine the scale, morphology, and orientation of the input cleave of the fiber without resorting to separate and more complex methods like optical imaging or scanning electron microscopy. Further, after obtaining the transverse scan of the fiber tip one can precisely position the focal spot anywhere relative to the fiber structure.     

Complex microwave susceptibility of a ferrofluid with Mag-Hematiteparticles: nonreciprocal phenomena in magnetic liquids

We present susceptibility measurements on a ferrofluid in the microwave frequency range with three different measurement cells: a coaxial line, an X-band rectangular waveguide, and an X-band slab-loaded rectangular waveguide. We use the reflection/transmission method to obtain the complex susceptibility χ^*. We have subjected the cells to a constant magnetic field applied parallel or transversal to the propagation direction. We observe an increase of the gyromagnetic resonance phenomenon and some discrepancies between the consequences of a parallel or transverse applied field. Nonreciprocal phenomenon has been observed for the first time in a ferrofluid when a transversal field is applied to an X-band slab-loaded rectangular waveguide     

Highly-efficient single-cell capture in microfluidic array chips using differential hydrodynamic guiding structures

This paper presents a highly efficient single cell capture scheme using hydrodynamic guiding structures in a microwell array. The implemented structure has a capturing efficiency of >80%, and has a capacity to place individual cells into separated microwells, allowing for the time-lapse monitoring on single cell behavior. Feasibility was tested by injecting microbeads (15 μm in diameter) and prostate cancer PC3 cells in an 8×8 microwell array chip and >80% of the microwells were occupied by single ones. Using the chips, the number of cells required for cell assays can be dramatically reduced and this will facilitate overcoming a huddle of assays with scarce supply of cells.     

Gap acousto-electric waves in structures of arbitrary anisotropy

A theoretical study has been performed of the acousto-electric waves guided by an air gap between two identical piezoelectric crystals of arbitrary anisotropy. The permissible number of such gap waves traveling slower than all bulk modes in the structure has been established. The interdependence between the existence of these "subsonic" gap waves and surface acoustic waves on the mechanically free surface of crystals constituting the structure has been investigated. The occurrence of leaky gap waves also has been discussed. In addition, the specific features of the resonance reflection in gap structures caused by the excitation of leaky waves have been analyzed.     

Optical diagnostics of dynamic structures in shock waves

We demonstrate the possibility of applying optical diagnostics based on laser Doppler anemometry techniques and the laser imaging of dynamic density fields to the investigation of kinematic and structural parameters of shock waves and the properties of air perturbed by shock waves. Using the proposed methods, dynamic structures in the shock wave have been revealed and the velocity of their motion over the wave front has been determined. It is suggested that these dynamic structures have an oscillatory nature.     

Resonance reflection of acoustic waves in piezoelectric bi-crystalline structures

The paper studies the bulk wave reflection from internal interfaces in piezoelectric media. The interfaces of two types have been considered. Infinitesimally thin metallic layer inserted into homogeneous piezoelectric crystal of arbitrary symmetry. Rigidly bonded crystals whose piezoelectric coefficients differ by sign but the other material constants are identical. Analytic expressions for the coefficients of mode conversion have been derived. An analysis has been carried out of specific singularities arising when the angle of incidence is such that the resonance excitation of leaky interface acoustic waves occurs. The conditions for the resonance total reflection have been established. The computations performed for lithium niobate (LiNbO3) illustrate general conclusions.     

Modulation instability of surface magnetostatic waves in ferromagnet-dielectric-ferromagnet structures

It is theoretically demonstrated that a modulation instability of magnetostatic surface waves with respect to perturbations along the propagation direction is possible in a laterally magnetized coupled ferromagnet-dielectric-ferromagnet structure. In the case of a single mode excitation of the given structure, the modulation instability can develop due to a change in the character of dispersion. If two modes are excited in the structure, the modulation instability can develop as a result of nonlinear coupling.     

The role of macrophages in bioartificial nerve grafts based on resorbable guiding filament structures

A 10 mm gap in a rat sciatic nerve was bridged by a bioartificial nerve graft consisting of a silicone tube containing seven longitudinally placed filaments made of non-resorbable material (polyamide [Ethilon®]) or resorbable materials (polydioxanon [PDS®], polyglactin [Vicryl®] or catgut). The purpose was to study the tissue reaction induced by the four different types of materials. At 4 weeks an immunocytochemical technique, using ED1 and ED2 monoclonal antibodies, was used to study the presence and location of macrophages. A large number of macrophages were found accumulating on the surface of catgut and polyglactin, while few were found on the surface of polyamide and polydioxanon filaments. It is concluded that the cell layers on the filament surface mainly consisted of ED1 positive cells and their thickness depends on the filament materials.     

Dispersion characteristics of the surface electromagnetic-spin waves in ferrite-ferroelectric-dielectric-metal structures

Dispersion characteristics of the surface hybrid electromagnetic-spin waves propagating in a layered structure comprising a ferrite film on a ferroelectric plate and a metal screen at a certain distance from the ferroelectric plate surface were experimentally studied. The experimental data are compared to the results of calculations performed within the framework of a previously developed theory. The theoretical and experimental dispersion characteristics show good coincidence.     

Unloading waves and unloading failures in structures under impact loading

In studies of dynamic inelastic response of structures under high strain rates, a great deal of attention has been paid to inertia and strain rate effects. Most of the published works have concentrated upon the dynamic response during loading. However dynamic failure of structures is not unusual during unloading. Some examples are presented, including how “front spalling” can be caused by the interaction of the incident unloading/reverse plastic waves and the following incident elastic unloading waves; how the surface damage on the target in the form of annular short circumferential surface cracks is induced by the unloading Rayleigh surface waves, and how a series of stress unloading waves predominantly propagate in viscoelastic media due to relaxation effects. It is emphasized that more attention should be paid to studies on unloading waves, unloading constitutive relations and failure criteria.     

Detecting lamb waves with broadband acousto-ultrasonic signals in composite structures

Lamb waves can be produced and detected in ceramic matrix composites (CMC) and metal matrix composites (MMC) plates using the acousto-ultrasonic configuration employing broadband transducers. Experimental dispersion curves of lowest symmetric and lowest antisymmetric modes behave in a manner analogous to the graphite/polymer theoretical curves. In this study a basis has been established for analyzing Lamb wave velocities for characterizing composite plates. Lamb wave dispersion curves and group velocities were correlated with variations in axial stiffness and shear stiffness in MMC and CMC. For CMCs, interfacial shear strength was also correlated with the first antisymmetric Lamb mode.     

Anisotropy of the nonreciprocal linear birefringence in crystals

Results are presented of an experimental investigation of nonreciprocal linear birefringence (a difference between the phase velocities of counterpropagating waves having the same linear polarization) in lithium iodate and potassium dihydrophosphate crystals in a magnetic field. An original double-pass optical measuring system using two linear quarter-wave phase plates (Fresnel rhombs) is used to demonstrate a new method of studying the effect which can give a fairly high sensitivity and avoid accompanying effects. Pis’ma Zh. Tekh. Fiz. 24, 13–18 (February 26, 1998)     

The spectrum of dipole-exchange spin waves in tangentially-magnetized metal-ferroelectric-ferromagnet-ferroelectric-metal sandwich structures

An equation describing the dipole-exchange spin waves in tangentially magnetized metal-ferroelectric-ferromagnet-ferroelectric-metal symmetric planar sandwich structures has been derived within the framework of the Green function tensor formalism for the Maxwell field equations. Changes in the wave spectrum in response to variation of the layer structure parameters are theoretically studied.     

Highly efficient Y-junctions with arc-bend branch structures of sunlight guiding systems for indoor illumination

This paper proposes both symmetrical and asymmetric Y-junctions with arc-bend branch structures for auxiliary indoor-illumination applications. These arc-bend branch structures can be used as a concave-mirror-like light guide, to change the direction of beam propagation and also to converge the beam spread angle. Optical simulation results show that the proposed arc-bend Y-junctions can achieve an inner coupling efficiency, not including plastic/air interfaces, above 90% in both usages: beam combiner and splitter. Particularly, when the applied branch opening angle becomes large, this high optical efficiency becomes more significant than those of linear straight Y-junctions. Moreover, it is also confirmed that the coupling efficiency of the symmetric arc-bend junction can be as high as 90.0%, and the asymmetric coupling efficiency is 93.4%, even if the branch opening angle is quite large.