An analog of double electromagnetically induced transparency with extremely high group indexes

An asymmetric metamaterial exhibiting an analog of double electromagnetically induced transparency(EIT) in the middle-infrared region is reported.The metamaterial consists of two-layered arrays of Ushaped rings embedded in a medium,with the lower layer rotated by 90°.Our simulations demonstrate that both maximum group indexes are extremely high at the two EIT-like positions.The group index reaches about thrice the currently reported maximum value at the high-frequency EIT-like position.The transmittance at the two transparency positions also possesses extremely high Q factors,which is conducive to controlling the propagation of electromagnetic waves.     

产生纳米级暗中空光束的方法研究

用时域有限差分法，给出光纤头近场区电场强度模的空间分布.讨论了当光纤纤芯分别取不同尺寸时，对此空间光场强度的影响.要想得到较大范围的暗中空光束，必须增加光纤纤芯尺寸.并且，对光纤纤芯尺寸取一较大值和光纤中空区域尺寸取一较小值时的情况进行讨论，可得在光纤头附近可以出现与光纤中空区域尺寸大小相当的暗斑(10¹ nm量级).但是，暗中空光束中背景光较强.为此，将光纤的空心设计为金属. 发现此时中心暗斑的背景光明显减弱，在近场区域可获得较为理想的暗中空光束.如进一步缩小光纤中空区域尺寸，可以在光纤头附近获得暗斑更小甚至纳米量级的暗中空光束.为获得一种纳米量级的暗中空光束提供一种方法.     

基于虚拟示波器动态判别溶液浓度

根据液滴对光具有会聚的特点以及溶液浓度与其折射率有定量的对应关系，设计了基于虚拟示波器动态判别溶液浓度的光电测量方法．     

多层超薄薄膜介质光热辐射的三维理论研究

在柱坐标系下，以热传导方程及边界条件为基础，通过Hankel变换及逆变换，得到多层热单介质膜中的温度场.以特殊参数为例，对膜层为三层时的特殊情况进行讨论，得知对于高热 扩散率的薄膜材料，纵向和横向的热导率比值越大，相位的变化也越大.低热扩散率薄膜材 料，不同的纵向和横向的热导率比对光热信号的影响很小.同时，光吸收系数越小，频率变 化对相位影响越明显. 关键词： 多层 热单介质膜 温度场     

Negative Refraction of a Symmetrical π-shaped Metamaterial

A symmetrical π-shaped metamaterial is investigated. Numerical simulations exhibit the negative-refractive property of this structure. The complex refractive index n, wave impedance z, effective permittivity ε and effective permeability μ have been retrieved from the simulated S parameters. The negative-refractive band lies between 11.2 GHz and 13.05 GHz. The frequency band with high transmission with low loss occurs between 11.95 GHz and 12.5 GHz, which is helpful for practical applications. The mechanism of the electromagnetic resonance is also revealed.     

Properties of the 3D photonic nanojet based on the refractive index of surroundings

We exhibit a three-dimensional （3D） photonic nanojet based on a dielectric microsphere irradiated by a plane wave with the finite-difference time-domain （FDTD） method. We investigate the influence of the refractive index of the surrounding on the properties of the nanojet by simulating the electric field distributions in it. The simulation results show that, by optimally choosing the size of the sphere and the ratio of the refractive indices of the sphere and the surrounding, the focus point can occur just on the surface of the sphere even if the refractive index of the surrounding is changed. Additionally, the peak amplitude of the nanojet increases with increasing the refractive index of the surrounding. However, the decay length and the jet width of the nanojet decrease simultaneously. These effects may have potential applications in observation or manipulation of nano-objects such as antibodies in biology. In nanojet-enabled optical data storage, the photonic nanojet may be also helpful for improving data-storage capacities and retrieval speed by controlling the field amplitude, the decay length, and jet width of the nanojet.     

高灵敏银纳米棒阵列对农药啶虫脒的表面增强拉曼散射快速检测

The determination of pesticide residue on agricultural products is increasingly important.Exposure to pesticides can cause severe acute reactions in humans,including aplastic anemia and leukemia.In this work,we developed a rapid and sensitive method to detect acetamiprid pesticide residue based on surface-enhanced Raman scattering.Silver nanorod (AgNR) arrays were fabricated by oblique angle deposition technology and were used as SERS substrates.Prior to detection,the AgNR arrays were cleaned with nitric acid solution or a mixture of methanol and acetone.Compared to the unwashed AgNR arrays,the AgNR arrays washed with methanol and acetone shows a signal enhancement 1000 times greater than the unwashed AgNR array due to the effective removal of the impurities on its surface.The limit of detection of acetamiprid was determined to be 0.05 mg/L.In addition,the molecular structure of acetamiprid was simulated and the corresponding vibration modes of the characteristic bands of acetamiprid were calculated by density function theory.To demonstrate its practical application,the AgNRs array substrates were applied successfully to the rapid identification of acetamiprid residue on a cucumber''s surface.These results confirmed possibility of utilizing the AgNRs SERS substrates as a new method for highly sensitive pesticide residue detection.     

地方师范院校多学科交叉复合的光电专业培养模式的探索与实践

针对地方高师院校光电信息科学与工程专业建设和人才培养过程中存在的培养方案与培养目标不一致、评价体系不健全、师资队伍构建不合理等问题,以“理工文教”多学科交叉复合为核心,以提高学生实践能力为目标,以江苏师范大学光电信息科学与工程专业人才培养为例,提出一种多学科交叉复合人才培养模式.该模式主要突出人才培养过程中的实践创新能力,更加适应当地师范院校“地方性、应用性、师范性”的特色.     

Goos–H?nchen shifts in reflective phase-gradient-produced metasurfaces

We studied Goos–H?nchen(GH) shifts on a reflective phase-gradient-produced metasurface. Their analytical solutions were achieved for both TE and TM polarizations utilizing the generalized Snell's law. The calculated results show that the GH shifts are evidently affected by phase gradients and incident angles, which means that a certain range of GH shifts can be realized as long as an incident angle, phase gradient, and frequency are properly chosen. This offers an effective method for the control of GH shifts.     

Independent Modulation of Omnidirectional Defect Modes in Single-Negative Materials Photonic Crystal with Multiple Defects

Single-negative materials based on photonic crystal with multiple defect layers are designed and the free modulation of defect modes is studied. The results show that the multi-defect structure can avoid the interference between the defect states. Therefore, the designed double defect modes in the zero effective-phase gap can be adjusted independently by changing the thickness of different defect layers. In addition, the two tunable defect modes have the omnidirectional characteristics. This multi-defect structure with above-mentioned two advantages has potential applications in modern optical devices such as tunable omnidirectional filters.