38 lines
922 B
Matlab
38 lines
922 B
Matlab
clc
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clear
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%% User choices %%
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lambda = 1; % wavelentgh in um
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N = 2^9; % number of points
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Lz = 3000; % z-limit of visualization in um
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Lx = 300; % x-limit of visualization in um
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A = 0.8; % amplitude of the beam
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r = 30; % radius of the beam in um;
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%%%%%
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k0 = 2 * pi / lambda; % wavenumber
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dz = Lz / (N - 1);
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dx = Lx / (N - 1);
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dkx = 2 * pi / Lx;
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z = 0:dz:Lz;
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x = -Lx/2:dx:Lx/2;
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kx = -pi/dx:dkx:pi/dx;
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E = A * exp(-(x / r).^2); % Gaussian beam
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% E = A * rect(x / (2 * r)); % uniform beam
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dn = @(E) (10^-3) * abs(E).^2; % change of refractive index vs field
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I = zeros(N, N); % resulting intensity
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for n = 1:N
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E = exp(-1i * k0 * dn(E) * dz) .* ifft(fftshift(exp(-1i * sqrt(k0^2 - kx.^2) * dz) .* fftshift(fft(E))));
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I(n, :) = abs(E);
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end
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imagesc(z, x, rot90(I));
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title(sprintf("beam amplitude = %.1f. Beam radius = %.1f mm", A, r))
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xlabel("z, mm")
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ylabel("x, mm")
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colorbar |