Zero permittivity band characteristics in one-dimensional plasma dielectric photonic crystal

We consider the oblique propagation of electromagnetic waves in one-dimensional plasma dielectric photonic crystals, the superlattice structure consisting of alternating plasma and dielectric materials using transfer matrix method. Our results show that photonic band gaps for all polarizations can be obtained in one-dimensional plasma dielectric photonic crystals. These structures can exhibit a new type of band or gap, for the incidence angles other than normal incidence, near frequencies where the electric permittivity of the plasma layer changes sign. This new band or gap arises, from the dispersive properties of the plasma layer, only for TM polarized waves and its width increases with the increasing angle of incidence. This differential behaviour under polarization can be utilized in the design of an efficient polarization splitter. The band characteristic is affected by the plasma width, the plasma density, dielectric width, the dielectric constant of the dielectric medium and angle of incidence.     

大带隙二维三角格子光子晶体结构参数的优化设计

光子晶体结构设计优化是理论研究的一个重要内容.运用平面波展开法对圆柱、方柱及正六边柱构造的二维三角格子光子晶体的禁带进行仿真计算,讨论了介质材料分别为GaAs、Si和Ge情况下,柱子形状、旋转角度、填充比的变化对完全光子禁带的影响.发现:对于二维三角格子光子晶体,相对于介质柱,空气柱更易获得完全光子禁带;而相对于圆柱及...     

掺杂对一维光子晶体带隙传输特性的影响

 基于传输矩阵法,数值研究了掺杂对一维光子晶体带隙特征的影响。研究表明：掺杂时,禁带中心会出现一导带,导带深度会随着掺杂位置、杂质折射率的变化而发生变化。当晶体结构给定时,总存在一个掺杂位置,使其禁带中心的导带深度达到最深;而对于给定的掺杂位置,当杂质折射率为某特定值时,禁带中心同样也会出现一个深度最深的导带,这种特性可应用于滤波器件和光学谐振腔的设计。     

Modelling of multi-bodies in close proximity under water waves——Fluid resonance in narrow gaps

Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μ the damping coefficient and V the local averaging flow velocity) are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water waves.The numerical results are compared with experimental data available in the literature.The comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the res...     

Structural and electronic properties of neutral clusters Ga12X (X=C, Si, Ge, Sn, and Pb) and their anions from first principles

The structural and electronic properties of neutral and negatively charged Ga₁₂X (X=C, Si, Ge, Sn, and Pb) clusters are calculated by the first-principles method. The results show that the most stable symmetry depends on the doped atom rather than the geometry structure. However, the geometry symmetry plays an important role in calculating the energy gap. In addition, in the anionic clusters, the added electron would reduce the energy gap by about 0.4 eV. As for the density of states (DOS), clusters with the same symmetry show a similar trend of DOS. The major impact on DOS by adding an electron is the occurrence of relative energy shift.     

AunCu ( n =1-3)二元合金小团簇结构和稳定性的密度泛函研究

采用密度泛函理论(DFT) B3LYP 在SDD基组水平上对AunCu(n =1-3)二元合金小团簇各种可能的构型进行几何优化,预测了各团簇的稳定结构. 并对基态结构进行了研究,计算了平均结合能、最高占据轨道能级和最低空轨道能级以及两者间的能隙.结果表明掺杂Cu原子后使得AunCu(n =1-3)团簇的化学性质更稳定.     

用变温霍尔效应估测锑化铟的禁带宽度

通过变温霍尔效应实验获得锑化铟的霍尔系数随温度变化的数据,根据半导体的霍尔系数随温度的变化规律,计算出禁带宽度,并且着重讨论禁带宽度的两种求法,比较了两种方法的计算精度.     

4H-SiC中基面位错发光特性研究

本文利用阴极荧光(CL)和选择性刻蚀的方法对4H-SiC同质外延材料中基面位错的发光特性进行了研究. 结果表明螺型基面位错(B_TSD)和混合型基面位错(B_MD)分别具有绿光和蓝绿光特性,其发光峰分别在530 nm附近和480 nm附近. 从测试结果中还发现B_MD 的发光位较B_TSD有所蓝移,分析认为B_TSD位错芯附近原子沿伯格斯 关键词： 4H-SiC 基面位错 发光特性 禁带宽度     

石墨烯量子点的磁性及激发态性质

利用密度泛函理论在B3LYP/6-31G(d)基组水平上研究了具有zigzag边界的石墨烯量子点,结果表明不同大小的石墨烯量子点的基态都是具有磁性的自旋三重态.其磁性一方面来源于zigzag边界上占有凸出位置的碳原子,另一方面来源于带有孤对电子的碳原子.从整体上看,除6b结构外,其他结构的能隙随着苯环数量的增加逐渐减小,而附加电荷却使体系能隙明显减小.用含时密度泛函理论(TD-DFT)对能隙为3.83 eV的由六个苯环排列成的三角形结构进行了激发态的计算,发现第十七激发态强度最大,能量为3.93 eV,对 关键词： 石墨烯量子点 磁性 能隙 激发态