Fresnel coefficients for a layer of NIM

Reflection and transmission of traveling and evanescent waves by a layer of material with a negative index of refraction (NIM) is studied by means of the Fresnel coefficients. We derive their values in the “NIM limit”, and we show that this limit is consistent with the exact solution. It is also indicated that simply substituting the negative values of the relative permittivity and permeability of the NIM material into the exact solution leads to incorrect results for evanescent waves.     

Reflection–refraction of attenuated waves at the interface between a thermo-poroelastic medium and a thermoelastic medium

Phenomenon of reflection and refraction is considered at the plane interface between a thermoelastic medium and thermo-poroelastic medium. Both the media are isotropic and behave dissipative to wave propagation. Incident wave in thermo-poroelastic medium is considered inhomogeneous with deviation allowed between the directions of propagation and maximum attenuation. For this incidence, four attenuated waves reflect back in thermo-poroelastic medium and three waves refract to the continuing thermoelastic medium. Each of these reflected/refracted waves is inhomogeneous and propagates with a phase shift. The propagation characteristics (velocity, attenuation, inhomogeneity, phase shift, amplitude, energy) of reflected and refracted waves are calculated as functions of propagation direction and inhomogeneity of the incident wave. Variations in these propagation characteristics with the incident direction are illustrated through a numerical example.     

Energy flow in negative index materials

From Maxwell's equations, we compute the speed and the direction of propagation of active power refractedfrom air into a negative index material. We prove, both analytically and numerically that the power mayrefract positively even if phase fronts refract negatively. Considerations on the usage of ray optics inproblems involving negative index materials are drawn.     

Wave propagation inside one-dimensional photonic crystals with single-negative materials

The propagation of light waves in one-dimensional photonic crystals (1DPCs) composed of alternating layers of two kinds of single-negative materials is investigated theoretically. The phase velocity is negative when the frequency of the light wave is smaller than the certain critical frequency ω_cr, while the Poynting vector is always positive. At normal incidence, such 1DPCs may act as equivalent left-handed materials. At the inclined incidence, the effective wave vectors inside such 1DPCs do refract negatively, while the effective energy flows do not refract negatively. Therefore, at the inclined incidence, the 1DPCs are not equivalent to the left-handed materials.     

负折射率介质层中光波的相位和传输特性研究

针对在理解负折射率材料中光波的传播特性时相位的特殊性质 ,详细分析推证了负折射率介质中折射率、波矢k的大小和方向、空间坐标系以及波相相位互之间的关系。分析结果表明负折射率介质层中的波矢k的反常取向是由于其标量值为负 ;在统一的坐标系下 ,由该标量值参与数值计算和分析 ,k则由标量值和单位矢量k0 (k0 >0 )共同决定 ,而不必再考虑左、右手系的区别。在此基础上依据电磁场理论推导了光波在负折射率介质层中的传输矩阵 ,用以分析含有负折射率介质层的复杂薄膜系统的光学性质。初步计算结果显示含有负折射率介质层的膜系对TE和TM波的光谱特性都有显著改变     

Manipulating negative-refractive behavior with a magnetic field

We demonstrated a construction of negative-index material (NIM) with epsilon(eff)=mu(eff)=-1 employing ferrites only, with no metallic components. Our design of the NIM is motivated by recent coherent potential approximation results and corroborated by exact numerical calculation demonstrating the negative refraction of an electromagnetic beam, with equal incident and refraction angles, as well as by the slab imaging phenomena, with the source-image separation twice as the slab thickness. The ferrite only based scheme furnishes the fabricated NIM with magnetically tunable working frequency, less loss and the air-matched wave impedance.     

Optical bulk and surface waves with negative refraction

In materials with negative refraction, the direction of wave propagation is opposite to the direction of the wave vector. Using an approach that characterizes the optical response of a medium totally by a generalized dielectric permittivity, , we discuss the possibility of seeing negative refraction for optical waves in a number of nonmagnetic media. These include bulk waves in organic materials and in gyrotropic materials where additional exciton–polariton waves can have a negative group velocity. It is known that dispersion of surface waves can be engineered by tailoring a surface transition layer. We show how this effect can be used to obtain surface waves with negative refraction.     

Asymmetry in Negative Refraction of Nonlinear Waves

Recently, inwardly propagating waves (called antiwaves, AWs) in nonlinear oscillatory systems have attracted much attention. An interesting negative refraction phenomenon has been observed in a bidomain system where one medium supports forwardly propagating waves (normal waves, NWs) and the other AWs. In this paper we find that negative refraction (NR) in nonlinear media has an asymmetric property, i.e., NR can be observed only by applying wave source withproper frequency to one medium, but not the other. Moreover, NR appears always when the incident waves are dense and the refractional waves are sparse. This asymmetry is a particular feature for nonlinear NR, which can neither be observed in linear refraction processes (both positive and negative refractions) nor in nonlinear positive refraction. The mechanism underlying the asymmetry of nonlinear NR are fully understood based on the competition of nonlinear waves.     

Space-frequency dependence of the Horizontal structure of a sound field in the presence of intense internal waves

Sound propagation in a shallow sea is considered in the presence of a packet of intense internal waves. It is shown that horizontal refraction caused by these packets can lead to noticeable changes in the spectrum and spatial intensity distribution of a signal propagating approximately parallel to the wave fronts of internal wave packets.     

Wave refraction and backward magnon–plasmon polaritons in left-handed antiferromagnet/semiconductor superlattices

Characteristics of the bulk electromagnetic waves in teraHertz frequency region are examined in a left-handed superlattice (SL) which consists of alternating layers of nonmagnetic semiconductor and nonconducting antiferromagnetic materials. General problem on the sign of the refractive index for anisotropic media is considered. It is shown that the phase refraction index is always positive while the group refractive index can be negative when some general conditions are fulfilled. Effective permittivity and permeability tensors of the SL are derived for perpendicular and parallel orientation of the magnetic anisotropy axis with respect to the plane of the layers. Problem of anomalous refraction for transverse electric and transverse magnetic-type polarized waves is examined in such media. Analytical expressions for both the phase and group refractive indices are obtained for various propagated modes. It is shown that, in general, three different types of the refracted waves with different relative orientation of the phase and group velocity vectors are possible in left-handed media. Unusual peculiarities of the backward modes corresponding to the coupled magnon–plasmon polaritons are considered. It is shown, in particular, that the number of the backward modes depends on the free charge carrier's density in semiconductor layers, variation of which allows to create different frequency regions for the wave propagation.     

Total negative refraction in real crystals for ballistic electrons and light

It is found that there exists a category of material interfaces, readily available, that not only can provide total refraction (i.e., zero reflection) but can also give rise to amphoteric refraction (i.e., both positive and negative refraction) for electromagnetic waves in any frequency domain as well as for ballistic electron waves. These two unusual phenomena are demonstrated experimentally for the propagation of light through such an interface.     

Negative refraction and focusing of circularly polarized waves in optically active media

Analysis indicates that certain types of optically active media are capable of producing negative refraction and focusing of circularly polarized waves. It is established that a slab of such material acts just as Veselago's hypothetical left-handed media lens, providing subwavelength resolution as Sir Pendry's ideal lens, but for circularly polarized waves.     

Left-handed interfaces for electromagnetic surface waves

We show that surface electromagnetic waves (SEMWs) propagating along two-dimensional (2D) interfaces separating different metamaterials can behave analogously to 3D electromagnetic waves in either usual or left-handed media, depending on the permeabilities and/or permittivities of the two materials forming the interface. We derive the conditions when SEMWs carry energy opposite to the phase velocity. In analogy to three-dimensional (3D) left-handed media, we derive both an anomalous Cherenkov emission and a reversed Doppler effect. We also predict a negative refraction at the boundary between two different interfaces, which can be useful for perfect 2D lensing.     

Amphoteric refraction exhibited by anisotropic crystals

Amphoteric refraction of light ray at the interface between isotropic materials and anisotropic materials is analyzed. Depending on the incident angle, the refractive light ray can either refract positively or negatively. This amphoteric refraction phenomenon can be quite prevalent when the difference of the two principal refractive indices is large. The reflectance under various incident angles has also been calculated, and an experimental demonstration with a calcite crystal in air is presented.     

Scattering phenomenon of qP wave at the interface of FGPM and piezoelectric medium

The present paper aims to investigate the reflection and refraction of quasi-longitudinal (qP) waves at the welded interface between rotating piezoelectric and FGPM half-spaces. The equation of motion and constitutive relations for both the media have been used to derive the expressions for reflection and refraction coefficients for various reflected and transmitted waves. Also, the energy ratios (dependent on incident angle) are calculated. Moreover, the sum of all energy ratios is approximately unity at each value of incident angle which ensures that the law of energy conservation at the interface. Moreover, it is observed that the reflection and refraction coefficients of various reflected and transmitted waves depend not only on the incident angle but also on the material constants of the medium, parameters of the electric potential, initial stress as well as rotation parameters of the two media. A particular case has been deduced to validate the present study. This investigation may have possible applications in the areas of signal processing, transduction, frequency shifting (a change in the velocity of surface waves and controlling the selectivity of a filter compensation) of individual devices.     

Self-Action of Wave Beams Containing Shock Fronts

We briefly review the effects of nonlinear self-action of beams of strongly distorted waves containing steep shock fronts. The features of inertial self-actions of periodic sawtooth waves in quadratic nonlinear media without dispersion are discussed. These phenomena can be caused by an acoustic wind or thermal lens formed as a result of the nonlinear dissipation at the shock fronts. Instantaneous self-actions are analyzed on the examples of periodic trapezoidal waves, which are formed in cubic nonlinear media and contain alternating compression and rarefaction shocks, and a single-pulse signal containing a shock front. Mathematical models and solutions to the corresponding nonlinear equations are given. A qualitative comparison with optical self-action phenomena and with available experimental data is performed.     

惠更斯作图法分析双折射中e光的反常现象

在单轴晶体双折射中,e光会发生一些反常的折射现象如负折射、e光离散角、全反射现象等.与文献中普遍所采用的基于平面光波在晶体中传播的电磁理论特性求解的过程不同,本文则以更为直观的惠更斯作图法为出发点,利用几何求解,得出负反射临界角、e光离散角、全反射临界角,并加以说明和讨论.     

Anomalous wave propagation in quasiisotropic media

Based on boundary conditions and dispersion relations, the anomalous propagation of waves incident from regular isotropic media into quasiisotropic media is investigated. It is found that the anomalous negative refraction, anomalous total reflection and oblique total transmission can occur in the interface associated with quasiisotropic media. The Brewster angles of E- and H-polarized waves in quasiisotropic media are also discussed. It is shown that the propagation properties of waves in quasiisotropic media are significantly different from those in isotropic and anisotropic media.     

梯度负折射率介质中高斯光束传输特性的研究

导出了高斯光束在梯度负折射率介质中的ABCD矩阵,据此得到光束在此介质中的传输模型.并利用此模型分析了高斯光束在梯度负折射率介质中的传输特性,发现它能产生空间孤子及呼吸子形式的传输,并发现光束的束腰半径不一定是最小束宽半径.还研究了梯度系数对介质聚焦能力的影响,据此可以设计出相应聚焦能力所需要的折射率分布.最后分析了传输时高斯光束曲率半径的变化情况,与光束束宽半径的变化显著不同,曲率半径始终从无穷大开始,然后产生一个个周期性的变换.     

Optical Magnus effect in metamaterials fabricated from ferromagnetic microwires

In homogeneous negative phase velocity media, the Doppler and Cherenkov-Vavilov effects and the refraction and pressure of light are anomalous: they are inverse with respect to the corresponding effects in conventional media. Using the geometrical optics approximation, it is shown that the optical Magnus effect in inhomogeneous negative phase velocity media is also anomalous. The effect is demonstrated by considering a metamaterial consisting of parallel amorphous ferromagnetic microwires in a magnetic field. The metamaterial proves to be a left-handed one in the realistic region of the electromagnetic spectrum. The optical properties of such a left-handed medium can be controlled by the external magnetic field.