色散媒质中的理想匹配层吸收边界及其误差分析

根据色散媒质的性质及电磁波在不同媒质交界面上的反射的机理，证明并分析了在理想匹配层吸收边界中引入色散可实现有效吸收入射到吸收边界上的电磁波，从而达到减少时域有限差分法计算区域和计算误差的目的。     

非线性左右手媒质界面的Goos-Hänchen位移

 由均匀平面电磁波在左右手媒质界面满足的切向边界条件出发,推导了电磁波由线性传统媒质入射到非线性左手媒质时波的传播特性。利用时间延迟的方法,给出全反射情况下媒质界面非线性Goos-Hänchen位移表达式。分析了非线性左手媒质界面的侧向位移随入射角及入射波电场强度的变化关系,发现入射波场强对传输特性起决定作用:当入射波电场小于临界场强时,调节入射场强可以控制相应的侧向位移;当入射波电场大于临界场强时,不再满足全反射条件,部分入射波透射到非线性介质中。波导中加入非线性介质不仅可以调节侧向位移的大小,且可以实现对入射波场强的控制。     

非线性左右手媒质界面的Goos-H(a)nchen位移

由均匀平面电磁波在左右手媒质界面满足的切向边界条件出发,推导了电磁波由线性传统媒质入射到非线性左手媒质时波的传播特性.利用时间延迟的方法,给出全反射情况下媒质界面非线性Goos-Hǎnchen位移表达式.分析了非线性左手媒质界面的侧向位移随入射角及入射波电场强度的变化关系,发现入射波场强对传输特性起决定作用:当入射波电场小于临界场强时,调节入射场强可以控制相应的侧向位移;当入射波电场大于临界场强时,不再满足全反射条件,部分入射波透射到非线性介质中.波导中加入非线性介质不仅可以调节侧向位移的大小,且可以实现对入射波场强的控制.     

超声效应与超声刀

超声亦称超声波,是指频率高于人类听觉上限频率(约2×104Hz)的声波,其波长范围约为10-2~10-6m。超声波在媒质中传播时,由于声波和媒质间的相互作用,使媒质发生一系列物理和化学变化,也会出现一系列力学、光学、电学、化学等超声效应。超声产生这些效应的基本作用主要有三个:(1)线性交变的振动作用,是由于媒质在一定频率和声强的超声波作用下作受迫振动,而使媒质质点的位移、速度、加速度以及媒质中的应力等分别达到一定数值而产生一系列超声效应。(2)由于超声振动的非线性而产生锯齿波形效应和各种直流定向力(如辐射压力和平均粘滞力等),并…     

吸收媒质界面上反射束的非镜像纵向位移

导出可用于计算来自吸收媒的反射束之ｓ偏振及ｐ偏振的纵向焦位移值的两个表达式。计算表明，Ｆｐ是正值，即ｐ波沿反射方向漂移；Ｆｓ是负值，因而ｓ波沿相反方向漂移。若令消光系数为零，这两个表达式简化成Ｃｈａｎ和Ｔａｍｉｒ给出的但仅适用非吸收媒质的公式。     

金属微料—绝缘媒质复合体的远红外吸收

利用有效媒质理论计算金属微料－绝缘媒质的远红外吸收，发现当微粒形状均匀连续分布时，可使微粒表面等离子体出现共振吸收谱，进而使复合体的吸收峰宽化，这现象可导致复合体的远红外异常吸收。     

金属微粒-绝缘媒质复合体的远红外吸收

利用有效媒质理论计算金属微粒─绝缘媒质的远红外吸收，发现当微粒形状均匀连续分布时，可使微粒表面等离子体出现共振吸收谱，进而使复合体的吸收峰宽化．这现象可导致复合体的远红外异常吸收     

聚焦超声波在层状生物媒质中的二次谐波声场的理论与实验研究

基于Khokhlov-Zabolotkaya-Kuznetsov(KZK)方程，在频域提出了聚焦超声波在层状生物媒质中传播的理论模型，该模型计及生物媒质的吸收、非线性和边界，同时考虑声源的衍射对声传播的影响.数值研究了聚焦超声波的基波和二次谐波在层状生物媒质中的声传播，并与实验结果相比较.研究结果表明，此方法可以有效地描述聚焦超声波在层状生物媒质中的二次谐波声场. 关键词： 聚焦超声波 层状生物媒质 二次谐波     

声脉冲在多孔性媒质界面上的反射

本文在理论上分析球面脉冲声波在空气和理想的多孔性媒质界面上的反射问题。在声源为脉冲点源的情形下,给出反射脉冲声波的一般表示式。对以下三种情况做了较详细的分析:(1)声源和接收点在垂直于界面的同一直线上,半无限厚多孔性媒质;(2)声源和接收点在垂直于界面的同一直线上,多孔性媒质层;(3)掠射,半无限厚多孔性媒质。脉冲声波在媒质层上的反射是以声脉冲在媒质层内多次反射和透射来处理的。文中还给出实验结果和理论计算的比较。     

关于光波的复指数表示

本文从光波复指数表达式中位相因子正负号的含义出发，讨论了两种复指数表达式与琼斯矩阵、吸收媒质的复折射率以及吸收媒质表面光反射的偏振性质之间的关系．最后给出了两组相应的表达式以保持符号的一致性．     

线偏振光在手征负折射介质中的古斯汉欣位移特性研究

从理论上分析了手征负折射介质中的横向位移特性,给出了线极化波入射条件下发生全反射时的横向位移随入射角的关系曲线。当入射角处于两个本征波的临界角之间时,TE和TM分量对应的横向位移方向相反。而当入射角大于全内反射角时,两个分量都将朝着正方向发生横向位移。通过比较发现手征负折射介质中的古斯汉欣位移特性与常规介质和一般手征介质也有着很大的不同之处。     

Large negative Goos-Hanchen shift at metal surfaces

It has been previously established that for p-polarized light incident onto a semi-infinite absorbing medium, large negative Goos-Hanchen (GH) shifts can be expected in the case of weak absorption at incidence close to the Brewster angle. The effect has been demonstrated for certain semiconducting media at optical frequencies. Here we point out that similar phenomenon can take place for strongly reflecting and attenuating medium such as metal at IR frequencies, with large incident angles close to grazing incidence. Moreover, unlike the previously-studied case with semiconductors, the Brewster angle in the present case with metals plays an insignificant role in the possible hindrance of the observation of such large negative shifts.     

基于维格纳方程的电子的古斯-汉欣位移

通过求解电子的维格纳方程研究二维电子气中电子的输运性质.我们发现电子在倾斜入射到势垒界面并反射时,出现与光波类似的古斯-汉欣位移.通过维格纳方程可以得到电子的瞬态演化,不仅可以计算古斯-汉欣位移还能研究电子在势垒内部的运动轨迹以及出现稳定古斯-汉欣位移的时间.与稳定相位法得到的古斯-汉欣位移对比发现,考虑古斯-汉欣位移...     

Longitudinal shift and transformation of a Gaussian beam upon reflection from a thin film

Specific features of deformation of a Gaussian beam reflected from a thin film are studied on the basis of numerical analysis. A complex deformation of its profile is shown to be governed by three factors: by the character of behavior of the reflectance close to the angle of incidence, the Goos-Hanchen longitudinal shift, and by the shift in the direction of incidence of the beam, which is caused by the presence of the film-substrate interface. An approximate expression for the displacement of the “center of gravity” of the reflected beam is obtained.     

Simultaneously Large and Opposite Lateral Beam Shifts for TE and TM Modes on a Double Metal-Cladding Slab

We report simultaneously large and opposite Goos-Hanchen shifts for TE and TM beams on a double metalcladding slab. Theoretical examination shows that both positive and negative lateral shifts are in two orders of the wavelength. It is also found that the magnitude of the lateral beam shift strongly depends on the thickness of the upper metal layer. The optimal thickness of the upper metal layer for zero reflection is found to be the critical thickness above which a negative beam shift occurs. Numerical calculations are in good agreement with the theoretical results.     

吸收介质界面上反射高斯束的角位移

给出高斯入射束反射时角位移直接计算式，适用于任意入射角和反射介质有吸收的情况。计算式在布儒斯特角上不存在发散困难，对于Ｐ偏振和Ｓ偏振均适用，只要令ｇ１＝ｎ１，ｇ２＝０计算所得即为Ｓ偏振的角位移。     

Large and negative Goos-Hänchen shift near the Brewster dip on reflection from weakly absorbing media

Applying Artmann's formula to a light beam in the TM state of wave polarization, we show analytically the existence of a large and negative Goos-H?nchen shift near the angle of the Brewster dip on reflection from a weakly absorbing semi-infinite medium. The shift is opposite that in the case of total internal reflection, and it can be an order of magnitude larger than a wavelength if the absorption of the reflecting medium is sufficiently weak. Examples are given, and the detectibility of the shift is discussed.     

Spatial soliton optical switches: a soliton-based equivalent particle approach

The spatial soliton plays a fundamental role as a robust, particle-like object which can be manipulated to switch or spatially scan collimated light channels or optical pulses which are incident at an oblique angle to an interface separating two or more selffocusing Kerr slab dielectrics. The underlying equivalent particle/multiparticle theory can also be employed to predict stability properties of nonlinear surface or guided waves, to derive an analytic expression for the nonlinear Goos-Hanchen shift at a nonlinear interface and to quantify the effect of material diffusion, linear and twophoton absorption on the switching behaviour of the light beam. Pulsed spatial switching effects are studied in order to illustrate the general predictive power of the equivalent particle theory.     

Control of direction of Goos–Hänchen shift on reflection from a weakly absorbing medium

The Goos–Hänchen effect of reflected beams at the interface between isotropic medium and weakly absorbing medium was studied. We find that there is a lateral shift when a light beam travels through the interface for reflected beam for TM wave. The influence of permeability and permittivity on the Goos–Hänchen shift was discussed, respectively. When the weakly absorbing medium is right-handed material the imaginary of magnetic permeability will control the direction and magnitude of the shift. On the contrary, when the weakly absorbing medium is left-handed material, the refractive index of the isotropic medium determines the direction and magnitude of the shift.     

Giant positive and negative lateral shifts from the Kretschmann-Raether configuration with a weakly absorbing left-handed slab

The lateral shift of a TE-polarized beam reflected from the Kretschmann-Raether structure with a weakly absorbing left-handed slab is studied theoretically. It is shown that the lateral shift can be very large negative as well as positive near the resonant condition. These large negative and positive shifts can be one order of magnitude much larger than the shift from the corresponding nonabsorbing slab. As the absorption factor increases, the incident angle of producing largest lateral shift increases when the thickness is kept unchanged but the thickness of the slab of producing largest lateral shift decreases when the incident angle is kept unchanged.