形状双折射金属表面等离激元的特征长度

针对p偏振,研究形状双折射金属和常规介电材料界面的表面等离激元(SPP)。基于形状双折射金属介电常数的双轴各向异性和SPP的色散关系,分别在X方向和Y方向讨论SPP波长、传播距离以及在两种介质中的穿透深度等特征长度的变化规律。另外,分别讨论形状双折射金属的3个结构参数对SPP特征长度的影响,发现X方向的结构周期变化只影响Y方向的SPP特征长度,Y方向的结构周期变化只影响X方向的SPP特征长度,纳米孔半径的变化同时影响X方向和Y方向的SPP特征长度。     

内嵌凹槽的金属亚波长狭缝共振透射特性分析

在亚波长金属狭缝内嵌入凹槽后,狭缝的透射峰发生红移、蓝移,也可能不变。本文利用有限时域差分法,详细讨论了内嵌凹槽深度对狭缝透射光谱的影响。通过与腔共振模式理论对比,我们发现内嵌凹槽的亚波长金属狭缝透射峰变化一方面来自于共振腔长度的增长,另一方面来自于透射峰所对应的共振模式数的增加。透射峰蓝移等变化均为共振模式数改变和共振腔长度增长共同作用的结果。     

利用亚趋附深度Ag膜在双层金属孔径阵列中实现一个显着的透射增强

本文采用理论和实验研究了利用亚趋附深度Ag膜在(Ag@Au)双层金属孔径阵列中实现的一个显着的透射增强现象,这是由于通过倏逝波使银/金界面中的表面等离激元（SPP）耦合作用的结果。结果表明,增强透射率是高度依赖Ag膜的厚度。当Ag膜厚度的增加,透射率峰值先增大,然后减小。此外,其他金属材料的性能也进行了讨论。当Ag膜的厚度为4 nm时,得到一个最高的透射率峰值。时域有限差分法（FDTD）模拟与实验结果吻合良好。这一发现提供了一种有效的方式来控制双层金属孔阵列的增强透射特性,在设计一个高性能的等离子体热发射器方面具有潜在的应用价值。     

Characteristics of highly sensitive terahertz wave detector based on lithium niobate

The characteristics of a highly sensitive terahertz wave detector based on lithium niobate have been investigated using a steady-state theory. The contributions of the low-frequency modes to the dielectric constant of lithium niobate are considered. The intrinsic factors of the LN detector limit its high frequency response to about 4?THz. Temperature dependence of the detector from room temperature to 250°C was also studied. The main factors associated with the temperature variations of the sensitivity of the detector are thermal expansion, the nonlinear coefficient and the refractive index of the crystal. The nonlinear coefficient dominates the temperature dependence of the sensitivity of the detector, while the impact of the refractive indices of the near-infrared lights on the temperature variation of the sensitivity of the detector is negligible. This study provides a useful guide and a theoretical basis for the further improvement of the detection systems.     

金纳米颗粒在石英基片上的表面等离子激元效应研究

采用磁控溅射法制备了金纳米颗粒,分别用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和紫外可见分光光度仪(UV-Vis)对其形貌、结构和光谱响应进行性能表征,研究其表面等离子激元效应。结果表明,直接在石英基片上溅射制备的金纳米颗粒并未产生表面等离子激元效应;在石英基片上组装单层排列均匀的Si O2微球后,溅射制备的金纳米颗粒结构产生了明显的表面等离子激元效应;溅射功率和时长对这一效应影响明显,40 W功率溅射2~3 min所得样品吸收峰较强。     

表面等离子体激元透镜设计及其数值计算

提出了一种新的表面等离子体激元透镜的设计方案,该方案通过在两个亚波长小孔的外表面放置电介质光栅实现对入射光束的有效会聚。利用遗传算法研究了波导中表面等离子体激元的色散关系,结果表明,通过调节亚波长小孔的宽度和介电常数可以有效地调控有效折射率,从而实现对亚波长金属平板波导结构中表面等离子体激元传播特性的调控。利用时域有限差分方法(FDTD)结合完美匹配层(PML)边界条件数值模拟了此结构中的光场分布,讨论了光栅周期数对成像特性的影响,从而深入理解了纳米聚焦效应的物理机制。结果显示,随着表面光栅数的增多,焦距和焦斑大小都在增加。光栅数从5增加至11时,焦距由1.715μm增大至2.325μm,焦斑大小由0.615μm增大至1.715μm,这一结构有可能被用作未来集成光路中的纳米聚焦器件。     

Strong coupling between surface plasmon polaritons and Sulforhodamine 101 dye

We demonstrate a strong coupling between surface plasmon polaritons and Sulforhodamine 101 dye molecules. Dispersion curves for surface plasmon polaritons on samples with a thin layer of silver covered with Sulforhodamine 101 molecules embedded in SU-8 polymer are obtained experimentally by reflectometry measurements and compared to the dispersion of samples without molecules. Clear Rabi splittings, with energies up to 360 and 190 meV, are observed at the positions of the dye absorption maxima. The split energies are dependent on the number of Sulforhodamine 101 molecules involved in the coupling process. Transfer matrix and coupled oscillator methods are used to model the studied multilayer structures with a great agreement with the experiments. Detection of the scattered radiation after the propagation provides another way to obtain the dispersion relation of the surface plasmon polaritons and, thus, provides insight into dynamics of the surface plasmon polariton/dye interaction, beyond the refrectometry measurements.PACS: 42.50.Hz, 33.80.-b, 78.67.-n     

Spontaneous emission rate enhancement of nano-structured silicon by surface plasmon polariton

Surface plasmon polariton (SPP) is an attractive candidate to improve internal quantum efficiency (QE)of spontaneous emission (SE) from nano-structured silicon (Si) including nano-porous silicon (NP-Si...     

Theoretical studies of surface phonon polariton in wurtzite AlInN ternary alloy

In this study, we report the surface phonon polariton (SPP) characteristics of wurtzite structure aluminium indium nitride (Al_xIn_1 − xN) ternary alloys over the whole Al composition range. An anisotropic model is used to simulate the surface polariton (SP) dispersion curves of the Al_xIn_1 − xN ternary alloys. The characteristics of these dispersion curves are discussed in detail and the effects of the composition dependence of the Al_xIn_1 − xN on the SPs are illustrated and explained. Moreover, the relevant experimental information from the attenuated total reflection (ATR) method is also presented, namely, the corresponding ATR spectra are simulated based on the standard matrix formulation. Through this study, it has been found that the SPP mode of the wurtzite Al_xIn_1 − xN exhibits mixed-mode behaviour.     

Studies of surface and interface phonon polariton characteristics of wurtzite ZnO thin film on wurtzite 6H-SiC substrate by p-polarized infrared attenuated total reflection spectroscopy

The surface and interface phonon polariton characteristics of a wurtzite ZnO thin film grown on a wurtzite 6H-SiC substrate are investigated by p-polarized infrared attenuated total reflection spectroscopy. Two absorption dips corresponding to the leaky surface phonon polariton (SPP) mode of ZnO and the interface phonon polariton (IPP) mode of ZnO/6H-SiC are clearly observed at 558 and 916 cm^− 1, respectively. The observations are in good agreement with the results determined from the theoretical surface polariton dispersion curve simulated by means of an anisotropy model. Finally, the effects of the ZnO thin film thickness on the SPP and IPP modes are deduced from the theoretical calculations.