作者机构：
[袁志; 朱卫华; 王新林; 陈志勇; 郭玮; 刘辉] School of Electrical Engineering, University of South China, Hengyang, Hunan, China;[王新林] School of Mechanical Engineering, University of South China, Hengyang, Hunan, China
通讯机构：
[Wang, X.-L.] S;School of Electrical Engineering, University of South China, Hengyang, Hunan, China
关键词：
亚波长金属孔阵列;增强光透射;时域有限差分;单元结构对称性;表面等离激元
摘要：
采用三维时域有限差分方法,对比研究了石英基底上周期性亚波长圆形、纽扣形、半圆形和太极形四种具有不同对称性的孔阵列微结构金属膜的增强光透射特性,并分别探讨了阵列周期、小孔尺寸对这四种阵列结构透射特性的影响.结果表明增强光透射特性对单元结构对称性具有很强的依赖性：在超短高斯光脉冲激励下,随着单元结构对称性的降低,归一化透过率逐渐增大,红外波段的透射峰发生大量红移,且其与可见光波段的透射峰之间的距离逐渐增大,在对称性破缺的太极形孔阵列中两峰间距最大,可达1 300 nm左右.表面等离激元模式与局域表面等离子体共振模式在增强光透射现象中起着重要的作用.在可见光波段,表面等离激元模式是这四种阵列结构的光透射增强的主导性因素;在红外波段,局域表面等离子体共振模式对单元结构对称性较差孔阵列结构的增强光透射特性有着显著影响. 3D finite-difference time-domain method was employed to comparatively study the enhanced optical transmission of four kinds of periodic subwavelength hole arrays metallic films,such as circular-shaped,button-shaped,semicircular-shaped and Tai-Chi-shaped holes which had different symmetries and were deposited on a quartz substrate. The effect of the hole arrays periodicity and the hole size on the enhanced optical transmission of these four array structures were investigated. The results show that the enhanced optical transmission is strongly dependent on the symmetries of unit cells. Under the excitation of ultrashort Gauss light pulse,the normalized transmission increases gradually with the reduction of unit structural symmetries,the transmission peak in infrared wavelengths range undergoes a large spectral red-shift. The distance between the transmission peak in visible and infrared wavelengths range increases gradually. The largest distance of 1 300 nm is in symmetry breaking Tai-Chi-shaped arrays. The surface plasmon polaritons mode and the localized surface plasmon resonance mode play important roles in the process of the enhanced optical transmission. In visible wavelengths,the surface plasmonic polaritons mode is the dominant factor to the enhanced optical transmission of these four arrays structures. In infrared wavelengths,the localized surface plasmon resonance mode significantly affects the enhanced optical transmission of the hoel arrays in poor unit symmetries.
摘要：
煤矿井下人员定位系统种类千变万化，但主要是在硬件和软件上的差异，因此，选择合适的硬件结构和软件架构会有效地避免井下巷道复杂，环境恶劣，干扰严重等因素.本文设计的基于NXP最新推出的集成片上TOF引擎的JN5168无线微控制器的井下人员定位前端控制系统，支持IEEE802.15.4无线通信协议，只需要设计芯片正常工作必要的外围电路，再通过改进TOF ( Time of Flight)测距软件定位算法，便可构成一个精确定位系统.该系统满足成本低、开发时间短、定位误差低、功耗低、实时性快等优点，对煤矿井下复杂环境的人员定位系统的研制具有一定的理论和应用价值.
摘要：
Finite-difference time-domain (FDTD) method is employed to study the optical properties of a novel kind of periodic subwavelength hole arrays composed of Tai-chi-shaped holes in silver film, and the optical transmission properties of femtosecond optical pulse excitation is numerically calculated. We find that this Tai-chi-shaped device has better optical band-pass filtering properties, such as narrower pass band and higher transmissivity in visible wavelengths range, than other devices under consideration. Based on the generation of surface plasmons resonance mode in the dielectric-metal interface, the center wavelength of transmission can be tuned by changing the array periodicities. We observe that the tune ability mainly depends on the space period along the direction parallel to that of the incident pulse polarization. It is also found that both the strength and the wavelength of the transmission peaks of rectangularly distributed metal hole arrays are determined by the polarization of incident light. Additionally, we demonstrate the typical band-pass filtering properties of this Tai-Chi-shaped holes structure. The full-width at half-maximum (FWHM) of the narrow pass band is about 20 nm in visible wavelengths range. (C) 2014 Elsevier B.V. All rights reserved.
摘要：
运用结合双温模型的分子动力学方法, 数值模拟了脉宽为100 fs的超短脉冲激光烧蚀B2结构镍钛形状记忆合金薄膜的作用, 研究了较低能量密度下B2结构镍钛形状记忆合金靶材的相变过程。结果表明, 超快激光与B2结构镍钛形状记忆合金相互作用时, 压力波传播引起了热能的弛豫。脉宽为100 fs, 功率密度为20~35 mJ/cm2的激光与靶材作用时, 烧蚀产生的压力波在其传播过程中诱导靶材发生了相变, 并形成三明治结构。 Incorporating with molecular dynamics method of two-temperature model, the effect of B2 structure Ni-Ti shape memory alloy film ablated by femto-second laser with 100 fs ultra-short pulse width is simulated in number and the phase transition of the target with lower energy density is researched. The results show that thermal energy relaxation is caused by the propagation of pressure wave when ultra-high speed laser interacts with B2 structure Ni-Ti shape memory alloy. The laser with 100 fs pulse width and 20~35 mJ/cm2 power density interacting with the target, the phase change of the target is induced by the pressure wave from ablating process during propagation. And a sandwich structure is formed.
摘要：
3D finite-difference time-domain method (FDTD) is carried out to simulate femtosecond optical pulses incident on silver film perforated by subwavelength holes arrays. Both square arrays and hexagonal arrays of nanoholes in silver film are considered. It is found that optical transmittance of square arrays almost does not vary with the polarization direction of incident light, while optical transmittance of hexagonal arrays varies obviously, especially when the wavelength equals the periodicity of holes arrays. This will be important for applications of novel optical devices.
作者机构：
[林英华; 文向东] School of Mechanical Engineering, University of South China, Hengyang 421001, China;[陈志勇; 李月华; 朱卫华] School of Electrical Engineering, University of South China, Hengyang 421001, China;[王新林] School of Mechanical Engineering, University of South China, Hengyang 421001, China<&wdkj&>School of Electrical Engineering, University of South China, Hengyang 421001, China
通讯机构：
[Lin, Y.] S;School of Mechanical Engineering, University of South China, China
