Optical coupling effects in semiconductor micro- and nano-structures

随着微纳米加工技术的不断发展，人们已经能够利用半导体技术，实现对微纳米尺度结构的精确制作。微纳米尺度下，光子与其它粒子间的相互作用更加明显，得到了科技领域的广泛关注。本文研究了半导体－金属界面等离子激元与半导体内功能性微纳米结构中复合光子的耦合作用，和半导体光子晶体中的微纳米功能性结构间的光耦合特性。采用时域有限差分算法模拟半导体－金属界面等离子激元的产生，及其与半导体内部电子和空穴之间的相互作用。分析了不同尺度金属电极对半导体发光器件内部功能性微纳米结构内电子－空穴对的复合发光的影响，进而揭示了紫外LED器件p型电极尺度对发光性能的影响。同时，结合平面波展开法和时域有限差分算法，研究了在半导...With the continuous profound developing of micro- and nano-processing technology, micro- and nano-structures have been achieved accurately in semiconductors. Recently, there has been much interest in the interaction between the photon and other particles in the micro- and nanometer scale. In this thesis, we focus our attention on the optical coupling effects in semiconductor micro- and nano-struct...学位：理学硕士院系专业：物理与机电工程学院物理学系_凝聚态物理学号：1982007115233

Structural design of communication filters using two-dimensional photonic crystals with defect modes

采用平面波展开法分别模拟设计了理想和带有点缺陷与线缺陷的二维光子晶体能带结构;进一步构建具有点缺陷和线缺陷联合结构滤波器,通过改变介质折射率、介质柱半径和背景材料折射率,使点缺陷的滤波中心波长处于光子晶体禁带中的1.31和1.55μm两个主要通迅波长.同时,采用时域有限差分算法模拟滤波器的传播和滤波频谱特性,结果显示,该结构滤波器的滤波频谱中心波长刚好分别位于1.31和1.55μm,透射峰尖锐,显现出优良的滤波特性.The band structures of 2D photonic crystals without and with point and line defects were simulated using plane wave expansion method.By calculating different index and radius of lattices,the 2D photonic crystal structures combining a point and a line defects were successfully designed to have modes in 1.31 and 1.55μm.The optical transmission and leaching characteristics of the designed structures were simulated by finite-difference time-domain(FDTD) method.The results show that the leaching spectra are shape and centered at 1.31 and 1.55μm,respectively,which suggests the designed structures are good to apply to the communication filters.“863”计划资助项目(2006AA03A110);; 基础科研资助项目(A1420060155);; 国家自然科学基金资助项目(60336020);; 厦门市科技计划资助项目(3502Z20063001

The impacts of accelerated erosion on soil nutrient loss and microbial quantity following deforestation in the Ziwuling area

以浅沟集水区为研究对象,分析了子午岭地区林地被开垦破坏15年后裸露地在不同侵蚀强度和侵蚀方式下的土壤养分流失和土壤微生物数量的变化。结果表明,林地开垦破坏后,土壤侵蚀加剧发展,侵蚀强度达159.7t/(hm2.a),是林地土壤侵蚀量的上千倍。开垦破坏15年后,裸露地浅沟集水区不同地形部位表层土壤全氮、有机碳、速效磷和土壤微生物总数显著减少,同林地相比,依次分别减少37.9%~82.6%、42.7%~86.4%、24.2%~80.3%和31.8%9~2.0%。在裸露地浅沟集水区梁坡随坡长的增加,表层土壤有机碳、全氮和速效磷含量及微生物总数呈显著的下降趋势,且沟槽的土壤各养分含量及微生物总数明显低于沟间。裸露地浅沟集水区土壤养分流失强度及微生物数量减少幅度在浅沟集水区的空间分布与土壤侵蚀方式和侵蚀强度相对应。林地开垦破坏15年后,土壤养分以有机碳流失最严重,其次分别为速效磷、全氮;微生物中的真菌减少幅度最大,细菌次之,放线菌减少幅度最小

Terahertz filters based on frequency selective surfaces for high-speed terahertz switch

Localized plasmon modes are excited and probed in a large-area grating-gate GaN/AlGaN high-electron-mobility transistor structure embedded in a Fabry-Perot cavity using a terahertz time-domain spectroscopy (THz-TDS) at cryogenic temperature. Determined by the length of grating finger and the electron concentration, the frequency of localized plasmon modes can be continuously tuned by the gate voltage in the spectral range from 0.1 THz to 1.5 THz. When the plasmon frequency is tuned to be in resonance with the terahertz Fabry-Perot cavity mode, a strong coupling between the plasmon mode and the cavity mode is observed and the terahertz plasmon-polaritons are formed in such a cavity-coupled two-dimensional electron system. The electromagnetic simulations have confirmed the strong coupling between them