Learning Forum

[JING PENG]

Hi Everyone,

Right now, I want to set up the orbital angular momentum (OAM) modes of the incident light in Lumerical FDTD. Does anyone know how to set the OAM mode of incident light?

It looks like that we can't set up this in the software itself, but we might be able to set it up in the lumerical script section. Below is an example of setting some parameters of the incident light, which I got online. It might a hint/reference to you.

Really hope someone can tackle this issue. Thanks.

# scriptfile:usr_custom_source.lsf

 

# define position vectors

 

x=linspace(-10e-6,10e-6,401);

y=linspace(-10e-6,10e-6,401);

z=0; #this is z z-normal source

 

X=meshgridx(x,y);

Y=meshgridx(x,y);

 

lambda0=0.5e-6;

f=c/lambda0;

w=2*pi*f;

k=2*pi/lambda0;

 

#calculate k-space field profiles

NA=0.2;

 

kx=linspace(-k,k,200);

ky=linspace(-k,k,200);

Kx=meshgridx(kx,ky);

Ky=meshgridy(kx,ky);

phi=atan2(Ky,Kx);

theta=real(acos(sqrt(1-Kx^2/k^2-Ky^2/k^2)));

envelope=exp(-0.5*(Kx^2+Ky^2)/(NA*k)^2);

 

Exk=cos(phi)*cos(theta)*envelope;

 

Eyk=sin(phi)*cos(theta)*envelope;

 

Ezk=sin(theta)*envelope;

 

Ex=-1i*czt(Exk,kx,ky,x,y);

 

Ey=-1i*czt(Eyk,kx,ky,x,y);

 

Ez=-1i*czt(Ezk,kx,ky,x,y);

 

Hxk=-sqrt(eps0/mu0)*sin(phi)*envelope;

Hyk=sqrt(eps0/mu0)*cos(phi)*envelope;

Hx=-1i*czt(Hxk,kx,ky,x,y);

Hy=-1i*czt(Hyk,kx,ky,x,y);

Hz=0*Ex;

 

# sacle fild so E^2=1

 

E2=abs(Ex)^2+abs(Ey)^2+abs(Ez)^2;

scaleFactor=sqrt(max(E2));

Ex=Ex/scaleFactor;

Ey=Ey/scaleFactor;

Ez=Ez/scaleFactor;

Hx=Hx/scaleFactor;

Hy=Hy/scaleFactor;

Hz=Hz/scaleFactor;

 

# package field data into the EM fields dataset

 

EM=rectilineardataset("EM fields",x,y,z);

EM.addparameter("lambda",c/f,"f",f);

EM.addattribute("E",Ex,Ey,Ez);

EM.addattribute("H",Hx,Hy,Hz);

 

# save dataset to .mat file

matlabsave("import_data.mat",EM);

[Guilin Sun]

This question has been replied here  请问和求教Lumerical FDTD 中如何设置入射光的光子轨道角动量OAM的问题   

Please note that there are limited number of standard sources in FDTD. However, with import, you can set up whatever the source you want.

[uzmayaqoob1960]

DEar Jing have u got any guidance how to impinge OAM source in Lumerical?

If yes then plz let me know too.

 

[Guilin Sun]

You have analytical solution for the OAM source. Please refer to this example https://optics.ansys.com/hc/en-us/articles/360034383054-Using-an-equation-to-define-the-spatial-field-profile-of-a-source-in-FDTD