基质折射率对反常色散散射体散射特性的影响

基于Mie散射理论,给出了散射强度、散射截面及吸收截面的计算公式,并对不同基质中碳化硅材料在反常色散区中的散射特性进行了数值计算与理论分析。结果表明,在反常色散区中,随着基质折射率的增大,散射强度的峰位发生红移,峰值增大;散射截面和吸收截面的峰位发生红移,峰值减小,这为该材料在反常色散区中的光学理论、实验及应用方面提供了理论参考。     

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.     

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。     

基于声光折射的聚焦超声焦点声压检测

提出了一种基于声光折射对聚焦超声焦点声压进行非侵入式检测的方法。当一束直径小于声波长的平行光束入射穿过聚焦超声的焦点时,通过研究焦点声压与光线偏转的具体关系,建立了光线最大偏转距离与焦点声压变化的关系模型,从而计算出焦点峰值声压。为了对理论模型进行验证,采用凹球面型聚焦换能器进行实验研究。通过与采用光纤水听器测量的结果进行对比,证明理论模型的可行性。结果表明实验得到的光斑图像与理论分析的结果一致,且用该方法测得的焦点峰值声压与光纤水听器测量的结果相比,相对误差小于15%,证明该方法具有可行性,能够定量检测焦点峰值声压。模型的提出也为将声光折射效应用于整个聚焦声场的定量检测提供了实验依据和理论依据。     

Excess permittivity and excess conductivity of binary fluid mixture isobutyric acid – water along the coexistence curve

Excess permittivity and excess conductivity of the binary fluid mixture isobutyric acid–water (I–W) have been computed at three temperatures and along the coexistence curve, on the basis of refractive index and electrical conductivity data of the mixture. The other related properties, molar volume, molar refraction and polarisablities have also been reported. The temperature dependence of the molar refraction was also examined. The results have been interpreted in terms of the nature of specific intermolecular interactions between the components.     

Viscous synergy and antagonism,excess molar volume,isoentropic compressibility and excess molar refraction of ternary mixtures containing tetrahydrofuran,methanol and six membered cyclic compounds at 298.15 K

The densities (ρ), viscosities (η), sound speeds (u) and refractive indices (n _D) of seven ternary mixtures of cyclic ether (tetrahydrofuran), methanoland cyclic compounds; benzene, toluene, chlorobenzene, nitrobenzene, anisole, cyclohexane and cyclohexanone are determined over the entire range of composition at 298.15?K. From the experimental observations, viscosity deviation (Δη), the viscous synergy and antagonism, synergic and antagonic index are derived by the equations developed by Kalentunc-Gencer and Peleg [G. Kalentunc-Gencer and M. Peleg, J. Texture Stud. 17, 61 (1986)] and Howell [N.K. Howell, Presented at the Proceedings of the Seventh International Conference, Wales, 1993], respectively. Excess molar volume (V ^E), excess isoentropic compressibility (ΔK _S) and excess molar refraction (ΔR) have been calculated from the experimentally measured density, sound speed and refractive index values. The excess Gibb's free energy of activation (ΔG ^E) has also been calculated. The results are discussed and interpreted in terms of molecular package and specific interaction predominated by hydrogen bonding.     

Dynamics of structural interfaces: Filtering and focussing effects for elastic waves

Dynamics of thick interfaces separating different regions of elastic materials is investigated. The interfaces are made up of elastic layers or inertial truss structures. The study of evanescent mode propagation and transmission properties reveals that the discrete nature of structural interfaces introduces unusual filtering characteristics in the system, which cannot be obtained with multilayered interfaces. An example of metamaterial is presented, namely, a planar structural interface, which acts as a flat lens, therefore evidencing the negative refraction and focussing of elastic waves.     

Coherent control of negative refraction based on local-field enhancement and dynamically induced chirality

This paper studies the electromagnetic response of a coherently driven dense atomic ensemble to a weak probe.It finds that negative refraction with little absorption may be achieved in the presence of local-field enhanced interaction and dynamically induced chirality.The complex refractive index governing the probe refraction and absorption depends critically on the atomic density,the steady population distribution,the coherence dephasings,and the frequency detunings,and is also sensitive to the phase of the driving field because the photonic transition paths form a close loop.Thus,it can periodically tune the refractive index at a fixed frequency from negative to positive values and vice versa just by modulating the driving phase.Moreover,the optimal negative refraction is found to be near the probe magnetic resonance,which then requires the electric fields of the probe and the drive being on two-photon resonance due to the dipole synchronisation.     

有机分子系统非线性折射的类透镜效应

采用分子系统的多能级结构讨论了有机分子系统非线性折射率随光强变化的规律及其正负变化的条件,分析了由非线性折射产生的正透镜效应和负透镜效应的相互转化现象,并采用Z扫描理论加以验证.     

Theoretical analysis of abnormal grain growth in HCP-polycrystalline thin films on rigid substrates

In this paper, the effects of grain orientation on preferred abnormal grain growth in HCP-polycrystalline thin films have been analysed with respect to strain energy. The calculated results showed that C_hkl, the average values of the orientation factor, decreased with increase of 1 for the same h and k and increased with increase of h or/and k for constant 1. Where (hkl) denoted a particular grain orientation, that is, the grains with (hkl) planes oriented parallel to the film surface. This is preannounced that, considering the strain energy solely, the grains with higher 1 and lower h and k should be favorable in HCP-polycrystalline thin films on rigid substrates after annealing.