2D (TM) dielectric cylinder(Y-axis infinity) - To simulate the scattering-absorption spectrum in optical range

The radius of cylinder is 200 nm (diameter = 400 nm), and the refractive index n=1.5. permittivity = n^2=2.25

Add the boundary of the CAD files (FreeCAD)

Reference : 3D-CAD Simulation & Examples

Due to FreeCAD default unit is mm, and in this case the sphere unit is nm. If use nm unit in FreeCAD, the resolution of output STL file will not enough. So, at here express

"the unit can directly transform between any unit, nm <=> um <=> mm "

FreeCAD:

diameter of cylinder: 0.4 mm = 400 um

length of the boundary: 1 mm = 1000 um

Define Parameters

A.Main-Setup

1. Selected the simulation dimension.

2. Define total x, y, z length that equal to CAD, and then set a appropriate resolution.

3. Import CAD files.

4. Define the material of each CAD.

5. Press【建立網格 Cad to Grids (Create)】button to create simulation grids.

* Dielectric Constant of cylinder define n^2 = 1.5^2 = 2.25,

(FreeCAD : um ==> FonSinEM : nm )

FreeCAD

diameter of cylinder: 0.4 mm = 400 um

length of the boundary: 1 mm = 1000 um

FonSinEM

Attention! the X, Z length define 1000, unit is nm

and the cylinder will be 400 nm in FonSinEM

"the unit can directly transform between any unit, nm <=> um <=> mm "

B.Boundary Conditions

A. Define the boundary conditions

B. Press the【創建 (Create)】button => Create the total grid size (Include the boundary condition & add space)

C.Wave & Observation

To simulate the Scattering-Absorption spectrum, select the (TFSF-RCS) radar cross section source

D. Geometries. Design

Checked out the simulation geometries, and then press 【輸出 Output】button to output the geometries files

Data_Materials.csv // (simulation index of structures)

E.Spectrum & Field Pattern

1. Set the Spectrum Analysis & Wavelength range

2. Check out the source

F.Calculation

1. Set the simulation time setp

2. Save parameters

3. Calculation

G.Result Analysis

★(Result Analysis)：

頻譜 (Spectrum) : Analysis the spectrum

Comparison of FonSinEM simulation results and analytical solution

Mie theory software

MieLab:

A Software Tool to Perform Calculations on the Scattering of Electromagnetic Waves by Multilayered Spheres

http://www.hindawi.com/journals/ijs/2011/583743/

Nmie:

https://nanohub.org/resources/8228

http://juluribk.com/2010/05/11/nmie-extinction-scattering-and-absorption-efficiencies-of-multilayer-nanoparticles/

This website contains many freeware，FDTD、FEM、Ray tracing method and mie theory codes

http://www.scattport.org/diogenes.iwt.uni-bremen.de/vt/scattport/index.php/light-scattering-software/mie-type-codes.html

====== Far-Field Diffraction Pattern Analysis=====

The near to far field transformation (NTFF) is a technology that to integrate the near field EM wave to the far-field diffraction pattern in FDTD algorithm. In FonSinEM, can use the "Pulse" and "Continue Wave (CW)" to do this. The difference between these is

In Pulse source, the observation range are fixed, but can obtain multi frequencies far field pattern at once calculation.

Menu ==> 【其它 Other】==>【遠場Far-Field】

In CW source, the frequency is fixed, but can change observation range arbitrary.

Use the steady state filed pattern analysis

following are the detail of these two NTFF method.

================== (Pulse) ================

1. Checked "Pulse" wave

2. Checked ☑近場觀測輸出 (Output NearField Ob.)-脈波 (Pulse Only)

The observation range will be defined automatically if the incident source type is TFSF-RCS.

Output the far-field values of the FonSinEM simulation

use the following code

csvwrite('scan_theta.csv',scan_theta)

csvwrite('RCS_theta.csv',RCS_theta)

csvwrite('RCS_phi.csv',RCS_phi)

The analytical solution code

MatScat

Author :Jan Schäfer

http://www.mathworks.com/matlabcentral/fileexchange/36831-matscat

scan_theta=csvread('scan_theta.csv');

RCS_theta=csvread('RCS_theta.csv');

RCS_phi=csvread('RCS_phi.csv');

%% Define test parameters

lambda0=400e-9;

dia = 400e-9;       % cylinder diameter

ns = 1.5 + 0.j;     % cylinder refractive index (complex)  epsr=ns^2

nm = 1;             % outer medium refractive index (real)

nang = 180;         % number of far field angles to evaluate

zeta = 90;          % cylinder inclination angle (90 deg = perpendicular)

[T, C, ang] = calccyl(dia/2., ns, nm, lambda0, nang, zeta);

fctr = 2/pi/C.k;

Far2E= fctr*squeeze(abs(T(2,2,:).^2));    % 2E

figure(1);hold on;

plot(scan_theta,RCS_theta(172,:),'r','Linewidth',3);

plot(ang, Far2E/max(Far2E(:))*max(RCS_theta(172,:)),'*b');

xlabel('Scattering Angle');

title('TM(ExEzHy)')

legend('FDTD','Analytical Solution')

Comparison of FonSinEM and Analytical solution

================== (CW) ================

Here choice the wavelength (lambda)=400 nm source of CW wave

Steady state field pattern analysis

Setup the observation range and then press the (NTFF Transformation) button

observation range : x=19,213, z=19,213 . In field pattern analysis, can change the observation range arbitrary

Output the far-field values of the FonSinEM simulation

use the following code

a(:,1)=scan_theta';

a(:,2)=RCS_theta';

a(:,3)=RCS_phi';

csvwrite('Far2DTM.csv',a)

The analytical solution code

MatScat

Author :Jan Schäfer

http://www.mathworks.com/matlabcentral/fileexchange/36831-matscat

load Far2DTM.csv

scan_theta=Far2DTM(:,1);

RCS_theta=Far2DTM(:,2);

RCS_phi=Far2DTM(:,3);

lambda0=400e-9;

%% Define test parameters

dia = 400e-9;  % cylinder diameter

ns = 1.5 + 0.j;     % cylinder refractive index (complex)  epsr=ns^2

nm = 1;         % outer medium refractive index (real)

nang = 180;         % number of far field angles to evaluate

zeta = 90;         % cylinder inclination angle (90 deg = perpendicular)

[T, C, ang] = calccyl(dia/2., ns, nm, lambda0, nang, zeta);

fctr = 2/pi/C.k;

Far2E= fctr*squeeze(abs(T(2,2,:).^2));    % 2E

figure(1);hold on;

plot(scan_theta,RCS_theta,'r','Linewidth',3);

plot(ang, Far2E/max(Far2E(:))*max(RCS_theta(:)),'*b');

xlabel('Scattering Angle');

title('TM(ExEzHy)')

legend('FDTD','Analytical Solution')

Comparison of FonSinEM and Analytical solution