Single & Double Slit diffraction
中文/English
Single Slit
Single Slit
Diffraction of single silt is a basically problem in optics.
Define Parameters
Define Parameters
Here considering a wave source wavelength = 300 nm, pass through a single silt with gaps = 1200 nm
1. Selected the simulation dimension.
1. Selected the simulation dimension.
2. Define total x, y, z length that equal to CAD, and then set a appropriate resolution.
2. Define total x, y, z length that equal to CAD, and then set a appropriate resolution.
3. Press【建立網格 Cad to Grids (Create)】button to create simulation grids.
3. Press【建立網格 Cad to Grids (Create)】button to create simulation grids.
A. Define the 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)
B. Press the【創建 (Create)】button => Create the total grid size (Include the boundary condition & add space)
select plane wave with linear polarization normal incident from bottom position z=21
select plane wave with linear polarization normal incident from bottom position z=21
1. Checked the simulation material that will be used
1. Checked the simulation material that will be used
2. Input the builtin function
2. Input the builtin function
3. Press the run button to execute the code
3. Press the run button to execute the code
4. Checked out the geometries
4. Checked out the geometries
5. If correct! then Press 【輸出 output】button to output the *.csv files.
5. If correct! then Press 【輸出 output】button to output the *.csv files.
Input a gap = 1200 nm single slit，material is perfect electric conductor (PEC)
Input a gap = 1200 nm single slit，material is perfect electric conductor (PEC)
%=================狹縫 Slit===========================lengthx=1200e-9; lengthz=100e-9; nindex=1^2;sigma=0;choice='PEC'; %E_Iso,PEC,M_Iso,PMC,E_Model1,M_Model1,EM_Model1gridtype=-1; %xposition=icenter*gdx;yposition=jcenter*gdy;zposition=100*gdz;Iso_Slit(choice,gridtype,nindex,sigma,xposition,zposition,lengthx,lengthz)%=================狹縫 Slit===========================Checked out the simulation geometries, and then press 【輸出 Output】button to output the geometries files
Checked out the simulation geometries, and then press 【輸出 Output】button to output the geometries files
Data_Materials.csv // (simulation index of structures)
Data_Materials.csv // (simulation index of structures)
instruction webpage: Built-in Function
instruction webpage: Built-in Function
★(Result Analysis)：
In finite difference time domain (FDTD) method, can use the near to far field (NTFF) technology to calculate far-field diffraction pattern.
In finite difference time domain (FDTD) method, can use the near to far field (NTFF) technology to calculate far-field diffraction pattern.
The diffraction of single slit can integrate the energy of the output gap side as shown in below. The left figure is sum a small ㄇshape, The right figure is sum a large ㄇ shape. Which one is correct?
The diffraction of single slit can integrate the energy of the output gap side as shown in below. The left figure is sum a small ㄇshape, The right figure is sum a large ㄇ shape. Which one is correct?
The answer : both are correct!
The answer : both are correct!
The NTFF setup at above figure, we checked ☑X-,☑X+,☑Z+
The range X from 200 => 400, Z from 103 => 180
in other words
☑X- range is x=200, Z=103:180
☑X+ range is x=400, Z=103:180
☑Z+ range is x=200:400, Z=180
This will be a ㄇ shape, and then press the【確定】button
To compare the far-field diffraction pattern of FonSinEM and theoretically solution
# Variable RCS_theta is built-in function
figure;plot(scan_theta,sqrt(RCS_theta),'r','linewidth',2.5);hold on;d=1200e-9;angles=linspace(-90,90,180);beta=1/2*2*pi/(lambda0)*d*sin(angles/180*pi);Intensity=abs(sin(beta)./beta);plot(angles,Intensity*max(sqrt(RCS_theta)),'*b','linewidth',0.5);title('\bf\it Far Field','Color','k','VerticalAlignment','bottom')xlabel('\bf theta','FontSize',12,'FontName','Arial','Color','b','VerticalAlignment','middle')ylabel('\bf intensity (a.u.)','FontSize',12,'FontName','Arial','Color','b')legend('FDTD','Analytical Solution') figure;polar(scan_theta'/180*pi,sqrt(RCS_theta),'r');hold on;polar(angles/180*pi,Intensity*max(sqrt(RCS_theta)),'b'); title('\bf\it Polar Plot (theta)','Color','k','VerticalAlignment','bottom')
Double Slits
Double Slits
1. Checked the simulation material that will be used
1. Checked the simulation material that will be used
2. Input the builtin function
2. Input the builtin function
3. Press the run button to execute the code
3. Press the run button to execute the code
4. Checked out the geometries
4. Checked out the geometries
5. If correct! then Press 【輸出 output】button to output the *.csv files.
5. If correct! then Press 【輸出 output】button to output the *.csv files.
Input a gap d = 1200 nm single slit，material is perfect electric conductor (PEC)
Input a gap d = 1200 nm single slit，material is perfect electric conductor (PEC)
d=1200e-9;b=d;%=================矩形 Brick===========================xstart=icenter*gdx-d/2;xend=icenter*gdx+d/2;ystart=1*gdy;yend=1*gdy;zstart=100*gdz;zend=100*gdz+100e-9;nindex=1^2;sigma=0;choice='PEC'; %E_Iso,PEC,M_Iso,PMC,E_Model1,M_Model1,EM_Model1gridtype=-1; %Iso_Brick(choice,gridtype,nindex,sigma,xstart,xend,ystart,yend,zstart,zend)%=================矩形 Brick=========================== %=================矩形 Brick===========================xstart=1*gdx;xend=icenter*gdx-b-d/2;ystart=1*gdy;yend=1*gdy;zstart=100*gdz;zend=100*gdz+100e-9;nindex=1^2;sigma=0;choice='PEC'; %E_Iso,PEC,M_Iso,PMC,E_Model1,M_Model1,EM_Model1gridtype=-1; %Iso_Brick(choice,gridtype,nindex,sigma,xstart,xend,ystart,yend,zstart,zend)%=================矩形 Brick=========================== %=================矩形 Brick===========================xstart=icenter*gdx+b+d/2;xend=ib*gdx;ystart=1*gdy;yend=1*gdy;zstart=100*gdz;zend=100*gdz+100e-9;nindex=1^2;sigma=0;choice='PEC'; %E_Iso,PEC,M_Iso,PMC,E_Model1,M_Model1,EM_Model1gridtype=-1; %Iso_Brick(choice,gridtype,nindex,sigma,xstart,xend,ystart,yend,zstart,zend)%=================矩形 Brick===========================
Other setups are all the same
Other setups are all the same
Result Analysis
Result Analysis
The NTFF setup at above figure, we checked ☑X-,☑X+,☑Z+
The range X from 30 => 570, Z from 103 => 180
in other words
☑X- range is x=30, Z=103:150
☑X+ range is x=30, Z=103:150
☑Z+ range is x=30:570, Z=150
This will be a ㄇ shape, and then press the【確定】button
To compare the far-field diffraction pattern of FonSinEM and theoretically solution
# Variable RCS_theta is built-in function
figure;plot(scan_theta,sqrt(RCS_theta),'r','linewidth',2.5);hold on;d=1200e-9;distance=2.*d; %兩狹縫中心距離angles=linspace(-90,90,360);beta=1/2*2*pi/(lambda0)*d*sin(angles/180*pi);Intensity=abs(sin(beta)./beta.*cos(pi/(lambda0)*distance*sin(angles/180*pi)));plot(angles,Intensity*max(sqrt(RCS_theta)),'*b', 'MarkerSize',5);title('\bf\it Far Field','Color','k','VerticalAlignment','bottom')xlabel('\bf theta','FontSize',12,'FontName','Arial','Color','b','VerticalAlignment','middle')ylabel('\bf intensity (a.u.)','FontSize',12,'FontName','Arial','Color','b')legend('FDTD','Analytical Solution')figure;polar(scan_theta'/180*pi,sqrt(RCS_theta),'r');hold on;polar(angles/180*pi,Intensity*max(sqrt(RCS_theta)),'b');title('\bf\it Polar Plot (theta)','Color','k','VerticalAlignment','bottom')