FDTD simulation of 260 nm thickness PAAO with Ag NPs in different mediums (AoI 45 deg., s- and p-polarizations)

FDTD software: Lumerical (Ansys, version 2021 R2.3). Structure: aluminum (Palik) substrate; 260 nm thickness (<em>h</em>) aluminum oxide (Palik) layer with 35 nm diameter (<em>RPo</em>) cylindrical pores with 100 nm distance (<em>D</em>) between the pore centers (representing porous anodized aluminum oxide - PAAO); 60 nm diameter (<em>AgRNP</em>) silver (Palik) nanoparticles (Ag NPs) placed directly above each pore. Refractive index of the surrounding medium (<em>n</em>): 1; 1.1; 1.2; 1.3. Simulation region: from 300 nm below the substrate/PAAO interface to 1.3 µm above PAAO surface; x and y spans are equal to one period of the structure. Mesh override region: from 50 nm below the PAAO to 50 nm above the nanoparticles; 2 nm step size in each direction. Light source: BFAST plane wave light source; 500 nm above PAAO; 45° angle of incidence (<em>ang</em>); 300 nm – 1000 nm wavelength range; s- and p-polarizations (<em>pol</em>). Monitors (frequency domain field and power): (1) 2D Z-normal; 1 µm above PAAO; results are in "<em>_reflection.txt</em>" files. (2) 2D Y-normal; centered to the structure; starts 50 nm below PAAO and ends 50 nm above nanoparticles; results are in "<em>.fsp</em>" files. (3) 2D X-normal; centered to the structure; starts 50 nm below PAAO and ends 50 nm above nanoparticles; results are in "<em>.fsp</em>" files. Information in the file name: <em>h</em> - thickness of PAAO; <em>pol</em> - polarization; <em>AgRNP</em> - diameter of silver nanoparticles; <em>RPo</em> - diameter of pores; <em>D</em> - distance between pore centers; <em>ang</em> - angle of incidence; <em>n</em> - refractive index of surrounding medium. Files: (1) "<em>_reflection.txt</em>" - lambda(nm) (first column) - wavelength in nanometers; Y (second column) - T data from the monitor above the structure. (2) "<em>_p0.log</em>" - log file produced by the software while running the simulation. (3) "<em>.fsp</em>" - Lumerical software file containing the simulation project; it can be used to extract data from Y- and X-normal monitors (license required to open these files). (4) "<em>Lumerical_Screenshots.pdf</em>" - shows software screenshots for every object and its every property; red text is added to show which values are different for different simulations. (5) "<em>Structure_Illustration.png</em>" - a schematic of modeled structure.时域有限差分（Finite-Difference Time-Domain, FDTD）软件：Lumerical（Ansys，版本2021 R2.3）。 结构参数：基底为铝（Palik）；其上沉积有厚度<em>h</em>为260 nm的氧化铝层（光学常数取自Palik数据集），该层带有直径<em>RPo</em>为35 nm的圆柱形孔，孔中心间距<em>D</em>为100 nm，此结构为多孔阳极氧化铝（Porous Anodized Aluminum Oxide, PAAO）；每个孔的正上方放置有直径<em>AgRNP</em>为60 nm的银纳米颗粒（Silver Nanoparticles, Ag NPs），其光学常数取自Palik数据集。 周围介质的折射率<em>n</em>取值为1、1.1、1.2、1.3。 仿真区域：从基底与PAAO的界面下方300 nm处延伸至PAAO表面上方1.3 μm处；x、y方向的计算跨度等于该结构的一个周期。 网格加密区域：从PAAO下方50 nm至纳米颗粒上方50 nm，各方向的网格步长均为2 nm。 光源：采用BFAST平面波光源，布置于PAAO上方500 nm处，入射角度<em>ang</em>为45°，波长覆盖范围为300 nm~1000 nm，包含s偏振与p偏振两种偏振态<em>pol</em>。 监视器（频域场与功率监视器）： 1. 2D Z法向监视器：布置于PAAO上方1 μm处，计算结果存储于"<em>_reflection.txt</em>"文件中。 2. 2D Y法向监视器：以结构中心为基准，范围从PAAO下方50 nm至纳米颗粒上方50 nm，计算结果存储于"<em>.fsp</em>"文件中。 3. 2D X法向监视器：以结构中心为基准，范围从PAAO下方50 nm至纳米颗粒上方50 nm，计算结果存储于"<em>.fsp</em>"文件中。 文件名所携带的参数含义如下：<em>h</em>为PAAO层厚度；<em>pol</em>为偏振态；<em>AgRNP</em>为银纳米颗粒直径；<em>RPo</em>为孔径；<em>D</em>为孔中心间距；<em>ang</em>为入射角度；<em>n</em>为周围介质折射率。 数据集包含以下文件： 1. "<em>_reflection.txt</em>"：数据文件，第一列为波长λ（单位：nm），第二列为结构上方监视器获取的T数据。 2. "<em>_p0.log</em>"：仿真运行时由Lumerical软件生成的日志文件。 3. "<em>.fsp</em>"：Lumerical软件专属的仿真工程文件，可用于提取Y、X法向监视器的相关数据，打开该文件需获得合法授权许可。 4. "<em>Lumerical_Screenshots.pdf</em>"：包含各仿真对象及其属性的软件截图，通过红色文本标注不同仿真间的差异参数。 5. "<em>Structure_Illustration.png</em>"：所建模的仿真结构示意图。