共查询到20条相似文献,搜索用时 15 毫秒
1.
V. A. Krakovskii 《Russian Physics Journal》1999,42(4):411-415
In the present paper the dispersion properties of surface magnetostatic waves (SMSWs) propagating in a stratified structure,
ferrite film—high-temperature superconducting layer, have been investigated. The problem of SMSW propagation in an inhomogeneous
stratified medium has been solved and the dispersion equation has been obtained. In the solution of this problem, the granular
nature of the high-temperature superconducting (HTSC) medium and the exposure to a constant magnetization field have been
taken into account. Upon exposure to the constant magnetic field the HTSC film becomes an inhomogeneous anisotropic medium
with respect to a variable magnetic field. The nonhomogeneous wave equation describing the SMSW field in a granular HTSC medium
has been solved by the method of sequential iterations. Corrections for the SMSW velocity and attenuation, calculated with
the use of the exact dispersion equation, are significant in comparison with previously obtained approximate values and exceed
20 and 40%, respectively. The method of analyzing electromagnetic fields in inhomogeneous granular high-temperature media
can be used to solve some other problems, where spatially inhomogeneous HTSC media are used.
Tomsk State University of Control Systems and Radioelectronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika,
No. 4, pp. 45–48, April, 1999. 相似文献
2.
应用经典场论和耦合模理论计算了斜向静磁场作用下,磁性薄膜波导中静磁波与导波光的相互作用.计算结果表明,与垂直静磁场情形相比,斜向静磁场时的相匹配条件有所变化,由于磁性薄膜波导中法拉第磁光效应增强等因素,导波光的Bragg衍射效率得以显著增加.这有利于应用YIG等低损耗磁性薄膜做成高衍射效率的磁光波导器件,亦有利于降低Bi∶YIG等高比法拉第旋转的磁光薄膜波导器件的体积和损耗.此外,理论指出的在斜向静磁场条件下所具有的一些磁光特性与实验结果亦符合得很好.
关键词: 相似文献
3.
Yu. P. Udoev 《Optics and Spectroscopy》2001,90(6):857-866
The two-wave approximation of the method of characteristics modes is used to analyze theoretically the diffraction of light by volume phase transmission gratings for arbitrary proportions between the average refractive index of the grating and the refractive indices of the ambient media. Simple expressions are derived for calculating the amplitudes of the diffracted waves in the case where the angle of incidence of the primary wave coincides with the Bragg angle. The roles of the front and back boundaries of the grating are discussed separately, and a new method for separating the contribution of the boundary diffraction, which is due to the periodic inhomogeneity of the grating boundaries, is proposed. The experimental possibility of selecting partial Bloch waves in the measurements of the diffraction efficiency of gratings that have high reflection coefficients of both boundaries is demonstrated. 相似文献
4.
S. Kuroiwa Y. Sugiyama H. Kawano-Furukawa 《Journal of Physics and Chemistry of Solids》2007,68(11):2129-2132
The small angle neutron scattering diffraction patterns from the flux line lattice state in the layered hexagonal superconductor CaAlSi are observed. Under an applied magnetic field (H) parallel to the crystalline c-axis, a hexagonal vortex structure is observed over the entire temperature/field regions. On the other hand, the vortex configuration under H∥a shows an ellipsoidal arrangement of the first-order Bragg peaks due to the anisotropic penetration depth. It was inferred from these results that the vortex state characterized by penetration depth and coherence length in CaAlSi may be described by that of anisotropic uniaxial superconductor using London theory. 相似文献
5.
I. Pallecchi M. Monni C. Ferdeghini V. Ferrando M. Putti C. Tarantini E. Galleani D'Agliano 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):171-179
Recent experimental data of anisotropic magnetoresistivity measured in
MgB2 films have shown an intriguing behaviour: the angular dependence
of magnetoresistivity changes dramatically with temperature and disorder. In
order to explain such phenomenology, in this work, we extend our previous
analyses on multiband transverse magnetoresistivity in magnesium diboride,
by calculating its analytic expression, assuming a constant anisotropic
Fermi surface mass tensor. The calculation is done for arbitrary
orientation of the magnetic field with respect to the crystalline axes and
for the current density either perpendicular or parallel to the magnetic
field. This approach allows to extract quite univocally the values of the
scattering times in the σ- and π-bands by fitting experimental data with a
simple analytic expression.
We also extend the analysis to the magnetoresistivity of polycrystalline
samples, with an arbitrary angle between the current density and the
magnetic field, taking into account the anisotropy of each randomly oriented
grain.
Thereby, we propose magnetoresistivity as a very powerful characterization
tool to explore the effect of disorder by irradiation or selective doping as
well as of phonon scattering in each one of the two types of bands, in
single crystals and polycrystalline samples, which is a crucial issue in the
study of magnesium diboride. 相似文献
6.
A. A. Stashkevich 《Russian Physics Journal》1989,32(4):241-261
We discuss the results of a theoretical analysis of the waveguide interaction of light and spin waves. Both linear and quadratic magnetooptical effects are taken into account. The features of the interaction are considered for the three principal types of spin waves: waves in a normally magnetized ferromagnetic film, and longitudinal and transverse waves in a tangentially magnetized film. Isotropic and anisotropic diffraction processes are considered. Numerical estimates of the intensity and frequency properties of the diffraction scattering are given for a number of situations of practical interest. The effect of a strong constant magnetic field on the interaction of light and spin waves is considered.Translated from Izvestiya Vyssnikh Uchebnykh Zavednii, Fizika, No. 4, pp. 5–31, April, 1989. 相似文献
7.
Light propagation in stratified anisotropic media with arbitrary orientation of optic axes smoothly varying from layer to
layer is considered. In the WKB approximation, a general expression for the field is obtained. For the case of a uniaxial
medium, the normal waves are found and specific features of the light propagation are analyzed. General conditions are obtained
that determine the turning points and forbidden zones. It is shown that the developed approach allows one to find trajectories
of rays in anisotropic media with arbitrary layered structure. 相似文献
8.
The scattering of polarized neutrons from magnetized samples is considered in the general case of arbitrary orientation between the incident polarization, the magnetic field of the sample and the polarization of the scattered neutrons. Including both nuclear and magnetic scattering the general expressions for the cross section and the polarization of the scattered beam are derived in the case of small-angle scattering. It is shown that under certain experimental conditions an effect analogous to the Neutron Spin Echo should be observed, which could be used to measure small energy transfers. The contribution arising from the scattering by spin waves is examined in detail. 相似文献
9.
P. Rose T. Richter B. Terhalle J. Imbrock F. Kaiser C. Denz 《Applied physics. B, Lasers and optics》2007,89(4):521-526
We investigate the formation of fundamental discrete solitons and dipole-mode gap solitons in triangular photonic lattices
imprinted in photorefractive nonlinear media. These lattices are strongly affected by the photorefractive anisotropy, resulting
in orientation-dependent refractive index structures with reduced symmetry. It is demonstrated that two different orientations
of the lattice wave enable the formation of fundamental discrete solitons in the total internal reflection gap. Furthermore,
it is shown that one lattice orientation additionally supports dipole-mode solitons in the Bragg reflection gap. The experimental
results are corroborated by numerical simulations using the full anisotropic model.
PACS 42.65.Tg; 42.65.Wi; 42.70.Qs 相似文献
10.
The subject of investigation is multiple-beam Bragg diffraction of light, i.e., the formation of a highly effective multiple-beam field representing a superposition of equidistant monochromatic acoustic waves with determinate phases and amplitudes using a nonaxial TeO2 deflector. It is shown theoretically and experimentally that the anisotropic character of interaction considerably changes the basic parameters of multiple-beam diffraction (compared with the isotropic case): the net diffraction efficiency grows to 100%, and the frequency band expands noticeably. A modulator splitting the initial laser radiation into five beams of equal intensity with a net efficiency approaching 100% is designed. 相似文献
11.
12.
The anisotropic Bragg diffraction of the volume holographic gratings in photorefractive crystals are investigated based on the model of anisotropic coupled-wave theory. The effect of the initial intensity ratio and the recording angles of the two recording waves on the anisotropic Bragg diffraction properties is discussed. It is shown that both the ratio of the initial intensity and the incident angles of the recording waves are selective action for the anisotropic Bragg diffraction efficiency of the volume holographic gratings, while these two recording conditions are not selective action for the isotropic Bragg diffraction. Furthermore, the Bragg phase matching condition of anisotropic diffraction is analyzed when the recording angles change. 相似文献
13.
This article presents a generalized vector plane wave expansion method, applicable to isotropic and anisotropic periodic dielectric media of arbitrary geometry and dimension. The influence of anisotropic material orientation on the symmetry properties of photonic crystal dispersion surface is discussed. It is shown that the overall Brillouin zone symmetry is formed by the intersection of the photonic crystal lattice symmetry and the symmetry determined by the anisotropic material orientation. This work explains how to define the irreducible Brillouin zone of a two-dimensional anisotropic photonic crystal and demonstrates that doing it correctly allows one to avoid erroneous results, when calculating band gap diagrams of anisotropic photonic crystals. With the help of the methods presented, the possibility of controlling the band gaps of anisotropic photonic crystals by means of external electric field is shown. 相似文献
14.
We put forward the existence of surface gap solitons at the interface between uniform media and an optical lattice with defocusing nonlinearity. Such new type of solitons forms when the incident and reflected waves at the interface of the lattice experience Bragg scattering, and feature a combination of the unique properties of both surface waves and gap solitons. We discover that gap surface solitons exist only when the lattice depth exceeds a threshold value, that they can be made completely stable, and that they can form stable bound states. 相似文献
15.
A. V. Andreev S. Yu. Stremoukhov O. A. Shutova 《Radiophysics and Quantum Electronics》2011,54(2):128-144
We develop the theory of interaction of the electromagnetic field and a single atom being in an arbitrary state and having
an arbitrary direction of the angular momentum of the atomic electron with respect to the direction of the field polarization
vector. It is shown that the atom response current has a tensor structure and depends on both the direction of the angular
momentum of the atom, and the polarization vector of the external field. The tensor character of the response is determined
by the externally induced anisotropic distribution of the probability density of spatial localization of the atomic electron.
It is shown that the induced-anisotropy effects clarify the harmonic generation mechanism at play during the non-resonance
interaction of laser radiation with atomic media. The developed theory is applied to the analysis of the problem about the
generation of terahertz waves in a two-color laser field. It is shown that the change in the mutual orientation of wave polarization
vectors leads to a significant increase in the efficiency of conversion of high-frequency fields to low-frequency ones. It
is shown for the first time that the generation of terahertz waves is possible in the preionization regime, when the generation
mechanism is related to atomic nonlinearity. 相似文献
16.
R. S. Akopyan A. V. Galstyan G. G. Zakharyan N. F. Vardanyan Yu. S. Chilingaryan 《Technical Physics》2006,51(6):752-757
The diffraction and polarization properties of thick anisotropic holographic gratings recorded in polymer-dispersed liquid crystals are studied experimentally and theoretically. Such gratings are anisotropic and sensitive to temperature variations and also exhibit a strong dependence of the diffraction properties on the incident radiation polarization because of the presence of liquid-crystal molecules. The dependences of the diffraction efficiency and diffracted beam polarization orientation on the diffraction grating temperature and incident beam linear polarization are obtained for the case of Bragg incidence. The same dependences are derived using the known experimental temperature curves of the liquid crystal permittivity. The experimental data are in agreement with the theoretical calculations. The feasibility of controlling the diffraction characteristics of the grating in a wide temperature interval is demonstrated. 相似文献
17.
We develop a physico-mathematical model describing excitation and distribution of electromagnetic waves in an anisotropic waveguide or resonator in the three-dimensional case. We develop a theoretical approach for discretization of the Maxwell equations in an arbitrary medium in the presence of bounding walls of a waveguide or resonator. The resulting system of linear algebraic equations for the electric-field components in an inhomogeneous anisotropic medium is solved by the method of biconjugate gradient. The results of calculating the electric field lines in the cross section of an anisotropic insert of a rectangular waveguide are presented. 相似文献
18.
An analysis is made of acoustooptic Bragg diffraction in a paratellurite crystal in the case of a slow shear acoustic wave. It is shown that the isotropic acoustooptic interaction in crystals has characteristic physical features, which distinguish it from the well-known anisotropic interaction. The isotropic interaction under study is shown to be a more complicated process than diffraction in optically isotropic media. A theoretical and experimental study of the dependences of Bragg angle of incidence on the ultrasound frequency was made. Expressions for the calculation of this dependence are presented, which give results that agree well with the experimental data. The dependences of the isotropic-diffraction efficiency on the acoustic power were studied. For the first time, it was found that the corresponding dependences for anisotropic and isotropic interactions are substantially different. It is shown that the isotropic interaction under study is weaker than the anisotropic interaction. However, the isotropic-diffraction efficiency has a noticeable value and can reach tens of a percent. 相似文献
19.
20.
Aranya B. Bhattacherjee 《Optics Communications》2009,282(17):3641-948
We investigate the interaction between a single mode light field and an elongated cigar shaped Bose-Einstein condensate (BEC), subject to a temporal modulation of the trap frequency in the tight confinement direction. Under appropriate conditions, the longitudinal sound like waves (Faraday waves) in the direction of weak confinement acts as a dynamic diffraction grating for the incident light field analogous to the acousto-optic effect in classical optics. The change in the refractive index due to the periodic modulation of the BEC density is responsible for the acousto-optic effect. The dynamics is characterised by Bragg scattering of light from the matter wave Faraday grating and simultaneous Bragg scattering of the condensate atoms from the optical grating formed due to the interference between the incident light and the diffracted light fields. Varying the intensity of the incident laser beam we observe the transition from the acousto-optic effect regime to the atomic Bragg scattering regime, where Rabi oscillations between two momentum levels of the atoms are observed. We show that the acousto-optic effect is reduced as the atomic interaction is increased. 相似文献