欢迎进入FDTD Solutions 的入门教程！入门教程由四章内容组成。
第一章介绍FDTD Solutions 的基本功能，以及器件建构，程序运行和结果分析。
后面三章则针对v个实际问题，提供详细指导，帮助用户一步步地了解每一模块的功能及其使用。
文中涉及的所有模拟设计文件都可以从LUMERICAL 的相应网页上免费下载。
第一章简介第二章银质纳米线谐振腔散射教程第三章环形谐振腔教程第四章光子晶体微腔教程简介The goal of the Getting Started Guide is to introduce the Finite Difference Time Domain (FDTD) technique and explain how modeling is done with the software.The FDTD algorithm is useful for design and investigation in a wide variety of applications involving the propagation of electromagnetic radiation through complicated media. It is especially useful for describing radiation incident upon or propagating through structures with strong scattering or diffractive properties. The available alternative computational methods - often relying on approximate models - frequently provide inaccurate results. FDTD Solutions is useful for numerous engineering problems of commercial interest including:• display technologies• optical storage devices• LED design• biophotonic sensors• plasmon polariton resonance devices• optical waveguide devices• photonic crystal devices• integrated optical filters• optical micro cavity designFDTD Solutions is an accurate and easy to use, versatile design tool capable of treating this wide variety of applications. This introductory chapter of the Getting Started Guide introduces the general FDTD method and provides a basic overview of the product usage. The final sections contain examples that are accompanied by step-by-step instructions so that you can set up and run the simulations yourself.什么是时域有限差分？The Finite Difference Time Domain (FDTD) method has become the state-of-the-art method for solving Maxwell’s equations in complex geometries. It is a fully vectorialmethod that naturally gives both time domain , and frequency domain information to the user, offering unique insight into all types of problems and applications inelectromagnetics and photonics .The technique is discrete in both space and time . The electromagnetic fields and structural materials of interest are described on a discrete mesh made up of so-called Yee cells . Maxwell’s equations are solved discretely in time, where the time step used is related to the mesh size through the speed of light. This technique is an exactrepresentation of Maxwell’s equations in the limit that the mesh cell size goes to zero. Structures to be simulated can have a wide variety of electromagnetic material properties. Light sources may be added to the simulation. The FDTD method is used to calculate how the EM fields propagate from the source through the structure . Subsequent iteration results in the electromagnetic field propagation in time. Typically, the simulation is run until there are essentially no electromagnetic fields left in the simulation region.Time domain information can be recorded at any spatial point (or group of points). This data can be recorded for the duration of the simulation, or it can be recorded as a series of "snapshots" at times specified by the user.Frequency domain information at any spatial point (or group of points) may be obtained through the Fourier transform of the time domain information at that point. Thus, the frequency dependence of power flow and modal profiles may be obtained over a wide range of frequencies from a single simulation.In addition, results obtained in the near field using the FDTD technique may be transformed to the far field, in applications where scattering patterns are important.More information about the FDTD method, including references, can be found in the Physics of the FDTD Algorithm section of the reference guide.FDTD的用户界面This section discusses useful features of the FDTD Solutions Graphical User Interface (GUI).In this topicGraphical User Interface: Windows andToolbarsAdd Objects to the simulationEdit ObjectsStart a new 2D/3D simulationGraphical User Interface: Windows and ToolbarsThe graphical user interface contains useful tools for editing simulations, including• a toolbar for adding objects to the simulation• a toolbar to edit objects• a toolbar to run simulations•an objects tree to show the objects which are currently included in the simulation• a script file editor window•an object library• a window to set up parameter sweeps and optimizationsIn the default configuration some of the Windows are hidden. To open hidden windows, click the right mouse button anywhere on the main title bar or the toolbar to get the pop up window shown in the screen shot below. The visible windows/toolbars have a check mark next to their name; the hidden ones do not have check marks. A second way to obtain the pop up window is to go to the main title toolbar and select VIEW->WINDOWS.For more information about the toolbars and windows see the Layout editor section of the reference guide.Add Objects to the simulationThe Graphical User interface contains buttons to add objects to the simulation. Click on the arrow next to the image to get a pull down menu which shows all the available options in a group. The screenshot below shows what happens when we click on the arrow next to the COMPONENTS button. Note that the picture on the button is the same as the MORE CHOICES option in the list. If we click on the button itself (instead of the arrow) we will go directly to the MORE CHOICES section of the object library.Also notice that the picture for the COMPONENTS button will change depending on what the last component that was added to the simulation was. Finally, the ZOOM EXTENTbutton in the toolbar will resize the viewports to fit all the objects currently included in the simulation.Edit objectsTo edit an object, select the object and press E on the keyboard or press the EDIT buttonon the toolbar. The easiest way to select an object is to click on the name of the object in the objects tree. However, objects can also be selected by clicking on the graphical depiction of them when the SELECT button is pressed. For more information see the Layout editor section of the reference guide.When we edit objects in FDTD, we get an edit window. The edit windows have units for the settings; in the GEOMETRY tab, the x, y and z location will be in μm by default. The units can be changed to nm if we choose SETTINGS->LENGTH units in the main menu. Fields in the edit windows act like calculators, so that equations can be entered in the fields. See the y span field below for an example.Start a new 2D/3D simulationBy default FDTD Solutions opens with a blank 3D simulation. In the following Getting Started Examples, we often begin with a 2D simulation, which can be obtained as shown in the screenshot below.模拟运行与优化This section discusses important checks which should be made before running a simulation (memory requirements, material fits) and gives links to more information about running simulations and parameter sweeps or optimizations.In this topicCheck memory requirementsCheck material fitsSetup parallel optionsRun simulationRun parameter sweeps and optimizationsCheck memory requirementsTo check the memory requirements, press the CHECK button If this is not the current icon, you can find it by pressing the arrow. Note that the memory report indicates the amount of memory used by each object in the simulation project as well as the total memory requirements. This allows for judicious choice of monitor properties in large and extensive simulations.Check material fitsThe CHECK button also contains a material explorer option . Many of the materials used in FDTD Simulations come from experimental data (see the materials section of the Reference Guide for references for the material data and descriptions of the FDTD material models). Before running a simulation, FDTD Solutions automatically generates a multi-coefficient model fit to the material data in the wavelength range for the source. It is a good idea to check and optimize the material fit before running a simulation. Setup the resource configurationBefore running any simulations, the resource options must be set up. These options canbe accessed by pressing the Resources button . In most cases, the default settings should be fine. The 'number of processes' is typically set to the number of cores in your computer.Run simulationYou can run simulations by pressing the RUN button on the mail toolbar. For more details, such as how to run multiple simulations in distributed mode, please see the RunSimulations section in the online User Guide, or the Running simulations and analysis section of the Reference Guide.Run parameter sweeps and OptimizationsFDTD Solutions also has a built in parameter sweep and optimization window. This window can be seen at the top of the page, and can be opened using the instructions in the Graphical User Interface discussion just prior to this topic.Optimization Window includes buttons to add a parameter sweep and add an optimization. Parameter sweeps and optimizations can include multiple parameters, or be nested. Each optimization or sweep can be run by pressing the right-most button.仿真数据分析This section discusses the tools used to analyze simulation data: the Analysis Window, the script environment and data export to third party software such as MATLAB. For more details please see the Analysis tools and the Scripting language chapters in the Reference Guide.In this topicAnalysis windowScriptingData exportAnalysis windowThe screen shot below shows the open analysis window. The analysis window can be used to plot monitor data.A variety of monitor data can be plotted via the Analysis window, depending on the monitor type. Spatial refractive index data, field vs time, field vs frequency, fields vs spatial dimensions, and power transmission vs frequency are a few examples. The terminology 'Intensity' indicates a squared quantity. For example, 'E intensity' means |E|^2. 'Ex intensity' means |Ex|^2. Field data from frequency monitors is always plotted as an Intensity. If you want to see the real or imaginary parts of the field, or if you want to obtain phase information, the scripting language will be required.ScriptingFDTD Solutions contains a built in scripting language which can be used to obtain simulation data, and do plotting or post-processing of data. The script prompt can be used to execute a few commands, or the built in script file editor can be used to create more complex scripts.A thorough introduction to the Lumerical scripting language can be found in the Scripting section of the FDTD Solutions online user guide. Definitions for all of the script commands are given in the Scripting language chapter in the Reference Guide.Data ExportFDTD simulation data can be exported into text file format using the analysis window, into a Lumerical data file format (*.ldf) which can be loaded into another simulation, or into a Matlab data (*.mat) file. Instructions for exporting to these file formats can be found in the links under the Scripting section.银质纳米线谐振腔散射教程问题综述当光波入射到金属纳米粒子上时，光与金属表面附近的电荷密度相互作用产生的表面等离子体极化surface plasmon polaritons 扮演着重要角色。
