Reply To: How Lumerical calculates the magnitude of P in the DFT monitor

[Afroditi Petropoulou]

Hello and thank you for contacting us,

 

Lumerical does indeed calculate P as E x H* as mentioned in Integrating the Poynting Vector – Ansys Optics.

I used the following script to get P directly from a 2D monitor (named it P_lumerical), to calculate P from E and H fields from the monitor (named it P_calculated) and to calculate the magnitude as sqrt(Px^2+Py^2+Pz^2) (named it P_magnitude) and finally to visualize all three of them.

 

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

mname="monitor";

 

E=getresult(mname,"E");

x=E.x;

y=E.y;

z=E.z;

f=E.f;

E=E.E;

 

H=getresult(mname,"H");

H=H.H;

 

P=getresult(mname,"P");

P=P.P;

Px=pinch(P,5,1);

Py=pinch(P,5,2);

Pz=pinch(P,5,3);

 

P_test=cross(E,conj(H));

Px_test=pinch(P_test,5,1);

Py_test=pinch(P_test,5,2);

Pz_test=pinch(P_test,5,3);

 

P_abs=sqrt(Px_test^2+Py_test^2+Pz_test^2);

 

P_lumerical = rectilineardataset("P_lumerical",x,y,z);

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

P_lumerical.addattribute("P_lum",Px,Py,Pz);

 

P_calculated = rectilineardataset("P_calculated",x,y,z);

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

P_calculated.addattribute("P_calc",Px_test,Py_test,Pz_test);

 

P_magnitude = rectilineardataset("P_magnitude",x,y,z);

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

P_magnitude.addattribute("P_mag",P_abs);

 

visualize(P_lumerical);

visualize(P_calculated);

visualize(P_magnitude);

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

 

In my example the results where the same.

 

Below the magnitude of P_lumerical and P_calculated is plotted:

 

The x component (by choosing X in “Vector operation”) of P_lumerical and P_calculated:

 

I also get the same results for y and z components.

 

The magnitudes of P_lumerical and P_magnitude also match:

 

Could you please tell me if the script gives you the correct results (the monitor name in the first line needs to be updated)?

 

I remain at your disposal for any further information.

 

Best regards,

Afroditi