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- %{
- Copyright © 2020 Alexey A. Shcherbakov. All rights reserved.
- This file is part of GratingFMM.
- GratingFMM is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation, either version 2 of the License, or
- (at your option) any later version.
- GratingFMM is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with GratingFMM. If not, see <https://www.gnu.org/licenses/>.
- %}
- %% description:
- % calculate grating vectors for 2D grating (periodicity in x and y directions)
- % and plane wave propagation constants in homogeneous media below and
- % above the grating
- %% input:
- % xno, yno: numbers of Fourier harmonics in X and Y dimensions
- % kx0, ky0: wavevector projections of an incident plane wave
- % kgx, kgy: wavelength-to-period ratios
- % eps1: permittivity of a medium below the grating (substrate)
- % eps2: permittivity of a medium above the grating (superstrate)
- %% output:
- % kz1: row of propagation constants in the substrate
- % kz2: row of propagation constants in the superstrate
- % kx: row of grating vectors in x-direction
- % ky: row of grating vectors in y-direction
- % kxy: row of grating vectors in xy plane
- %% implementation:
- function [kz1, kz2, kx, ky, kxy] = fmmtd_kxyz(xno, yno, kx0, ky0, kgx, kgy, eps1, eps2)
- [kx,ky] = meshgrid(kx0 + kgx*(linspace(1,xno,xno) - ceil(xno/2)), ...
- ky0 + kgy*(linspace(1,yno,yno) - ceil(yno/2)));
- kx = reshape(kx,1,[]);
- ky = reshape(ky,1,[]);
- kxy = kx.^2 + ky.^2;
-
- kz1 = sqrt(eps1 - kxy);
- kz2 = sqrt(eps2 - kxy);
- ind = angle(kz1) < -1e-12;
- kz1(ind) = -kz1(ind);
- ind = angle(kz2) < -1e-12;
- kz2(ind) = -kz2(ind);
- kxy = sqrt(kxy);
- end
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