Absorption of surface polaritons by molecules near the surface of a metallic slab

The cross section for absorption of surface polaritons (SP) by molecules above a metallic slab is calculated quantum mechanically. It shows a strong dependence on the thickness of the slab. This feature, even more pronounced, should also appear in more complex processes involving SP. It is also argued that SP guided by thin metallic films should be a useful tool in the spectroscopy of absorbates.     

Evolution of surface plasmon resonance with slab thickness in hybrid nano-structures of Au/InGaAs slab waveguide

We report on the evolution of the surface plasmon (SP) and waveguide mode (WM) as the core thickness is varied in InGaAs slab waveguides covered by metallic sub-wavelength slit arrays. By comparing transmission spectrum in the near-infrared region with numerical simulations, transmission dips were assigned to resonant excitations of either SPs or WMs. As the core thickness was smaller than the SP penetration depth, the resonance energy exhibits a blue shift, which scales with the field intrusion into the substrate region. For the core thickness of 400 nm supporting both the WM and SP, effective refractive index of the SP is almost constant due to the field decay within the InGaAs region, which is different to the case of the WM.     

Thickness dependence of the surface-polariton relaxation rates in a crystal slab

A few useful formulas are derived concerning the damping properties of long-wavelength surface polaritons (SP) in a crystal slab. For example, it is shown that the SP propagation length in a metal slab with thickness 2a satisfying $\text{ω}{}_{\mathrm{p}}\text{a}\text{c}\text{< 1}$ (c is the velocity of light and ω_p the electronic plasma frequency) is increased by the factor $\text{3}\text{2}\text{(}\text{c}\text{ω}{}_{\mathrm{p}}\text{a}\text{)}{}^4$ in comparison with the corresponding value for SP in a semi-infinite metal.     

Characteristics of plasmonic resonance in a sandwiched metamaterial nano film

We will investigate the surface plasmon (SP) resonances of a dielectric-sandwiched metamaterial thin film. The parameters of the metamaterial are chose so that it has both negative $\epsilon$ and μ in visible frequency range. We use transfer matrix method to calculate the attenuated total reflection (ATR) spectra of the layered system to investigate the variation of SP resonances and the associated resonance strength. The results show that, for both p- and s-polarized incident lights, the plasmonic resonances can be manipulated by changing the thickness of the metamaterial. Otherwise, the plasmonic resonance strength for each SP mode can be tuned to become a maximum with proper slab thickness and light frequency for both polarized lights.     

Effect of surface plasmon coupling with radiating dipole on the polarization characteristics of AlGaN-based light-emitting diodes

The optical polarization characteristics of surface plasmon (SP) coupled AlGaN-based light emitting diodes (LEDs) are investigated theoretically by analyzing the radiation recombination process and scattering process respectively. For the Al_0.5Ga_0.5N/Al/Al₂O₃ slab structure, the relative intensity of TE-polarized and TM-polarized spontaneous emission (SE) rate into the SP mode obviously depends on the thickness of the Al layer. The calculation results show that TM dominated emission will be transformed into TE dominated emission with the decrease of the Al thickness, while the emission intensities of both TE/TM polarizations will decrease significantly. In addition, compared with TM polarized emission, TE polarized emission is easier to be extracted by SP coupling. For the Al_0.5Ga_0.5N/Al nano-particle structure, the ratio of transmittance for TE/TM polarized emission can reach ～3.06, while for the Al free structure, it is only 1.2. Thus, the degree of polarization of SP coupled LED can be improved by the reasonable structural design.     

Revisiting the Balazs thought experiment in the presence of loss: electromagnetic-pulse-induced displacement of a positive-index slab having arbitrary complex permittivity and permeability

Over a half-century ago, Balazs proposed a thought experiment to deduce the form of electromagnetic momentum in a lossless and non-dispersive slab by imposing conservation of global momentum and system center-of-mass velocity after a pulse has traveled through the slab. Here, we revisit the Balazs thought experiment by explicit calculations of momentum transfer and center-of-mass displacement of a non-dispersive, positive-index slab of arbitrary complex permittivity and permeability using a set of postulates consisting only of Maxwell’s equations, a generalized Lorentz force law, the Abraham form of the electromagnetic momentum density, and conservation of both pulse and slab mass. In the case where the slab is lossless, we show that a pulse of arbitrary shape incident onto the slab conserves both global momentum and system center-of-mass velocity, consistent with the starting postulates of the Balazs thought experiment. In the case where the slab is lossy, we show, within the context of the above postulates, that global momentum is always conserved and that system center-of-mass velocity is conserved only when mass transfer from the pulse to the slab is described by an incremental pulse-mass-transfer model, proposed here, in which the pulse deposits mass in the slab with a distribution corresponding to the instantaneous mass density profile of the pulse.     

Imaging Properties of a Rectangular-Lattice Metallic Photonic-Crystal Slab

We report the imaging properties of a two-dimensional rectangular-lattice photonic crystal （PC） slab consisting of rectangular metallic rods immersed in a dielectric background. By simulating the electromagnetic wave propagation through such a PC slab with the finite-difference time-domain method, we find that a point source placed in the vicinity of the PC slab can form a good-quality image through the slab. The frequency region where a good-quality image is formed can be controlled by choosing the direction along which the PC slab surface normal is placed.     

不同厚度有耗左手材料板中的电磁波研究

 基于有损耗的Lorentz模型的时域有限差分（FDTD）方法,模拟了有耗左手材料（LHM）平板对波源的图像聚焦特性。分别计算了不同宽度的左手材料平板结构。通过比较说明电磁波在不同厚度左手材料板中传播方式相同。材料板越薄,其聚焦点的位置越往板边缘靠近。当左手材料板的厚度不满足聚焦尺寸时,该聚焦点将会消失。     

侧面抽运板状激光介质的热汇冷却

高热负荷固体激光介质的热效应已经成为制约激光器功率进一步提高的严重障碍,只有对激光介质进行有效的冷却才能保证其安全运行。以不均匀换热系数模型为基础,研究了具有非均匀内热源的侧面双向抽运板状激光介质在狭窄通道强制对流冷却情况下的耦合换热问题,对热汇冷却方案下介质的温度分布和热应力分布进行了数值模拟和分析,并对复合介质、蓝宝石和金刚石三种热汇材料进行对比。结果表明,忽视换热系数的非均匀性将导致应力计算结果偏低。对于侧面抽运、侧面冷却的激光介质,金刚石热汇冷却方案最佳,蓝宝石热汇方案次之,而复合介质方案不宜采用。     

激光二极管端面泵浦多段复合板条激光器热效应

针对激光二极管端面泵浦的多段渐变浓度复合板条激光增益介质,提出了两种选取掺杂浓度的方法,并分别计算了多段渐变浓度复合板条增益介质的热量、温度及应力分布.结果表明,与单一掺杂浓度板条增益介质相比,采用多段渐变浓度复合增益介质可显著降低增益介质内部的温度梯度及最大热应力,从而提高了激光器整体的损伤极限泵浦功率,有利于激光器的功率升级.     

激光二极管端面泵浦多段复合板条激光器热效应

针对激光二极管端面泵浦的多段渐变浓度复合板条激光增益介质,提出了两种选取掺杂浓度的方法,并分别计算了多段渐变浓度复合板条增益介质的热量、温度及应力分布.结果表明,与单一掺杂浓度板条增益介质相比,采用多段渐变浓度复合增益介质可显著降低增益介质内部的温度梯度及最大热应力,从而提高了激光器整体的损伤极限泵浦功率,有利于激光器的功率升级.     

单负介质薄板波导中的表面波模式

 推导了沿单负介质薄板波导传播表面波的特性,根据本征方程运用图解法得到沿介电常数为负的单负介质薄板传播的奇偶对称TM型表面波的色散曲线图和能流分布图。发现表面波在单负介质波导中传播比在双正或双负介质波导中慢,场和能量集中于介质板的上下表面, 一定频率范围内奇偶表面波型能流反向;单片单负介质板能实现功分器和定向耦合器的功能,简化了传统的复杂结构,在发展微波器件的小型化方面有着潜在的应用价值。     

Negative refraction and imaging properties of circular photonic crystals

The electromagnetic wave propagation in a two-dimensional (2D) circular photonic crystal (CPC) is investigated. The CPC structure is composed of air holes in the dielectric background material. The finite element method is used to study the optical and propagating properties of the CPC slab. Numerical simulations show that negative refraction and near-field imaging can appear in a 2D CPC slab. We also find that the high-symmetry CPC slab possesses an optics axis along the vertical direction intersecting the symmetric center. As a result, the CPC slab can exhibit an excellent imaging performance when a source is placed on the optical axis.     

二极管激光器侧泵浦波导耦合系统设计

 为了提高面阵二极管激光器侧泵浦板条激光器泵浦光的利用率，本文采用光线追迹的方法，通过数字模拟设计出了高耦合效率的波导耦合系统。实验测试结果表明，其耦合效率达到85%以上，泵浦光在板条内分布均匀。     

Magnetically driven Rayleigh-Taylor instability with acceleration gradient

We investigate the stability properties of a slab of accelerating, current-carrying, cold, fluid when the accelerating J_ /spl times/ B_ force is nonuniform throughout the slab and leads to a gradient in the slab acceleration. A nonuniform force that squeezes (stretches) the slab while accelerating it increases (decreases) the Magnetic-Rayleigh-Taylor instability growth rate. This effect can explain recent experiments on thin, magnetically driven, imploding liner shells.     

Negative Refraction and Near-Field Imaging of an Elliptical-Rod Photonic Crystal Slab in the Second Band

Negative refraction and imaging properties of the electromagnetic wave through a two-dimensional photonic crystal （PC） slab, which consists of a square lattice of elliptical dielectric rods immersed in the air background, is studied by the plane-wave expansion method and the finite-difference time-domain method. A point source placed in the vicinity of the PC slab can form a good-quality image spot through the PC slab for the incident frequencies within the second photonic band. The calculated result also shows that negative refraction occurs in this kind of PC slab.     

磁场中极性晶体板内的强耦合极化子

采用推广的强耦合变分波函数方法，研究了在板面垂直方向施加磁场的极性晶体板内电子与体纵光学声子和表面光学声子强相互作用系统的能量和有效质量，得出了作为厚度和磁场强度函数的极化子的能量和有效质量表达式．对Cu₂O材料作了数值计算，并讨论极化子的基态能、电子与声子相互作用能以及有效质量随板厚及磁场强度变化的规律 关键词：     

Scattering from a PEC strip buried in non-integer dimensional planar grounded dielectric slab by using Kobayashi potential method

Solution for electromagnetic scattering from a perfect electric conducting strip buried in a planar grounded dielectric slab is determined by using the Kobayashi Potential Method. It is assumed that the dimension of mediums, above and within the slab, is non-integer in the direction normal to interface of the slab. The scattering problem is divided into two parts. In the first part, fields in the absence of strip are determined for plane wave excitation. In the second part, presence of the strip is taken into account. It has been assumed that spacings between the strip and interfaces of the slab are comparatively very larger than the wavelength of monochromatic operating frequency. Due to this assumption, scattered field after reflection from the interfaces has no interaction with the strip. In order to gains more insight, several special cases of the geometry are treated. Using saddle point method, far-zone scattered field for region above the grounded slab is also determined.     

极性晶体膜中强耦合激子的性质

在强耦合极化子模型基础上,采用Lee-Low-Pines(LLP)变分法研究了极性晶体膜中激子与表面光学(SO)声子强耦合、与体纵光学(LO)声子弱耦合体系的性质.讨论了极性晶体膜中激子的诱生势与膜厚度和温度的变化关系.结果表明:激子的诱生势不仅与电子-空穴间距离有关,而且与极性晶体膜厚度有关,同时温度对激子诱生势的影响十分显著.     

应用干涉原理检测激光晶体夹具的应力

详细介绍了激光干涉原理,在此基础上,引入了一种简单实用的板条激光器夹具应力检测方法,从而减小了应力对板条激光器带来的不利影响。实验结果表明：夹具对板条各个方向产生的应力均匀,通过初步实验得到了6.94 W的1 064 nm连续光输出。