

June 5, 2024 at 6:33 pmLuca SacchiSubscriber
Hi,
I am simulating a library of pillars with RCWA following the example of Lumerical (https://optics.ansys.com/hc/enus/articles/360042097313SmallScaleMetalensFieldPropagation). Here is the picture of my simulation
The unitcell is subwavelength, so only the (0,0) order is dominant.
Since I am interested in the phase of the plane wave after the pillar I can either use the RCWAFieldMonitor positioned at a specific heigth from the pillar and take the phase of the field in the middle of the monitor. Otherwise I can use the values of the scattering matrix as in the example of lumerical:
grating_characterization = getresult("RCWA","grating_characterization");
n = find(grating_characterization.n, 0); # n index of 0th order
m = find(grating_characterization.m, 0); # m index of 0th orderSTpp(:) = pinch(grating_characterization.Tpp(:,1,n,m));
phase_Ep = angle(STpp);
My problem with this method is that I do not know at with distance from the pillar the phase is taken. While with RCWAfieldmonitor I know at which z I put the monitor, the scattering matrix method just gives me a value of the phase. I have three possible interpretation for phase_Ep: phase_Ep is the phase at the last RCWA interference defined (therefore the end of the pillar), phase_Ep is the phase of the field at the top boundary of the RCWA simulation region or phase_Ep is the phase of the field at "infinity". I tried to look for documentation but I was not able to find an answer.
To summurize: at which heigth in the simulation region is the phase extracted via the scattering matrix S defined?

July 2, 2024 at 10:42 pmGuilin SunAnsys Employee
Hi Luca,
Somehow my previous reply was not successfully shown. Here again is my reply:
RCWA is a semianalytical method with Fourier plane waves to decompose the physical fields in the device. Thus the phase reference of the amplitude coefficients is at the last/last material interface. The rest, eg the substrate and the superstrate will be considered as uniform, semiinfinite space.

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