Learning Forum

[A.Abdur Rahman Akib]

Hello, I was trying to design a metalens using P-B phase by rotating nanofins to get the 2pi phase change and I was using https://optics.ansys.com/hc/en-us/articles/360042097313-Metalens this design as my base, here I replaced the pillar by the nano fin. But I am not getting proper phase vs rotation, I am getting results just the screenshot uploaded.
P.S. I haven't change anything apart from the pillar, all other parameters and designs same as it is as the example. I really need help!

Do i need to change something in the S parameter I am really lost. 

[Guilin Sun]

It seems the interpolation might have errors, as the phase cannot be that large.

Please first test the example, make sure everything is duplicated. then change the unit cell to your own, plot the rotaion vs phase again.

 

Since the source and the monitors are in the same analysis group, make sure their locations are proper.You can also check if the transmission is correct.

 

[A.Abdur Rahman Akib]

To achieve berry phase I needed to use circularly polarized light, from a post in the forum I've came to know that lumerical can not calculate circularly polarized lights phase directly. 

Therefore first I ran the simulation for polarization angle 0 then 90 degree then took the phase difference of S.S21_Gn from angle 0 - angle 90

Is this the right approach? But I am still not getting proper results.

[Guilin Sun]

“To achieve berry phase I needed to use circularly polarized light, from a post in the forum I've came to know that lumerical can not calculate circularly polarized lights phase directly. ”

I do not think there is anything to prevent you calculating the phase of the phase of circularly polarized light. What you need to calculate is: get the complex ampltude of the decomposed cp light. It needs a little math.eg, the total fields are A*RCP+B*LCP.

[A.Abdur Rahman Akib]

clear;

load("unit_cell.fsp");

 

period = getnamed("::model","period");

 

# get data from sweep

sname= "radius";

radius = getsweepdata(sname,"radius");

height = getsweepdata(sname,"height");

S = getsweepresult(sname,"S");

phase = pinch(angle(S.S21_Gn),1,1); # the dimension of S21_Gn is [frequency,radius,height]

phase = pinch(unwrap(phase)) - phase(1);

height = height(1);

E = getsweepresult(sname,"E");

H = getsweepresult(sname,"H");

wavelength = E.lambda;

matlabsave("EH_and_phase_vs_radius_fdtd",wavelength,height,period,phase,radius,E,H);

 

#############################################################

# interpolate radius and fields on a denser phase data points

#############################################################

phase_interp = linspace(0,2*pi,361); # limit the phase range to 0 - 2*pi

radius_interp = spline(radius,phase,phase_interp); # phase sampled at an interval of 1 degree.

plot(phase_interp*180/pi,radius_interp*1e9,"phase (degree)","radius (nm)","","linewidth=2");

holdon;

plot(phase*180/pi,radius*1e9,"phase (degree)","radius (nm)","","plot type = point,marker type=x, color=red");

legend("radius_interpolated","radius from sweep");

holdoff;

 

E = getsweepresult(sname,"E");

Ex = pinch(E.Ex); Hx = pinch(H.Hx);

Ey = pinch(E.Ey); Hy = pinch(H.Hy);

Ez = pinch(E.Ez); Hz = pinch(H.Hz);

x = E.x;

y = E.y;

z = E.z;

f = E.f;

wavlength = c/f;

 

# interpolate over radius

Ex = interp(Ex,x,y,radius,x,y,radius_interp);

Ey = interp(Ey,x,y,radius,x,y,radius_interp);

Ez = interp(Ez,x,y,radius,x,y,radius_interp);

Hx = interp(Hx,x,y,radius,x,y,radius_interp);

Hy = interp(Hy,x,y,radius,x,y,radius_interp);

Hz = interp(Hz,x,y,radius,x,y,radius_interp);

 

# spatial sampling

######################

do_sampling = true;

ns = 3; # sampling per period

 

if (do_sampling) {

xs = linspace(min(x),max(x),ns);

ys = linspace(min(y),max(y),ns);

Ex = interp(Ex,x,y,radius_interp,xs,ys,radius_interp);

Ey = interp(Ey,x,y,radius_interp,xs,ys,radius_interp);

Ez = interp(Ez,x,y,radius_interp,xs,ys,radius_interp);

Hx = interp(Hx,x,y,radius_interp,xs,ys,radius_interp);

Hy = interp(Hy,x,y,radius_interp,xs,ys,radius_interp);

Hz = interp(Hz,x,y,radius_interp,xs,ys,radius_interp);

 

Ex = reshape(Ex,[ns,ns,1,1,length(phase_interp)]);

Ey = reshape(Ey,[ns,ns,1,1,length(phase_interp)]);

Ez = reshape(Ez,[ns,ns,1,1,length(phase_interp)]);

Hx = reshape(Hx,[ns,ns,1,1,length(phase_interp)]);

Hy = reshape(Hy,[ns,ns,1,1,length(phase_interp)]);

Hz = reshape(Hz,[ns,ns,1,1,length(phase_interp)]);

 

E = rectilineardataset("E",xs,ys,z);

E.addparameter("f",f);

E.addparameter("radius",radius_interp);

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

H = rectilineardataset("H",xs,ys,z);

H.addparameter("f",f);

H.addparameter("radius",radius_interp);

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

phase = phase_interp;

radius = radius_interp;

}

 

mat_pillar = getnamed("pillar","material");

index_pillar = getindex("pillar",c/wavelength);

mat_sub = getnamed("substrate","material");

index_sub = getnamed("substrate","index");

 

matlabsave("EH_and_phase_vs_radius_interp_fdtd",wavelength,height,period,mat_pillar,index_pillar,mat_sub,index_sub,phase,radius,E,H);

 

visualize(E);

 

 

 

[A.Abdur Rahman Akib]

I am using the uloaded code for phase calculation, is this code alright???

[A.Abdur Rahman Akib]

also in another post you've mentioned this method, i did not uderstand it fully, can you please explain this a bit, thank you for replying.