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gradient_glass.m

@@ -0,0 +1,48 @@
+clc
+clear
+
+%% User choices %%
+lambda = 1; % wavelength in um
+N = 2^10; % number of points
+Lz = 2000; % z-limit of visualization in um
+Lx = 600; % x-limit of visualization in um
+r = 60; % radius of the beam in um
+
+g_start = 500; % z-coordinate of the input surface of the glass
+g_end = 1500; % z-coordinate of the output surface of the glass
+p = 0.07; % parameter of the glass
+%%%%%
+
+k0 = 2 * pi / lambda; % wavenumber
+
+dz = Lz / (N - 1);
+dx = Lx / (N - 1);
+dkx = 2 * pi / Lx;
+
+z = 0:dz:Lz;
+x = -Lx/2:dx:Lx/2;
+kx = -pi/dx:dkx:pi/dx;
+
+E = exp(-(x / r).^2); % Gaussian beam
+%E = rect(x / (2 * r)); % uniform beam
+
+g_width = g_end - g_start; % width of the gradient glass
+dn = @(x, z) p * rect((z - g_start - (g_width / 2)) / g_width) * (x / Lx); % function of the gradient glass
+
+I = zeros(N, N); % resulting intensity
+for n = 1:N
+    E = exp(-1i * k0 * dn(x, dz*n) * dz) .* ifft(fftshift(exp(-1i * sqrt(k0^2 - kx.^2) * dz) .* fftshift(fft(E))));
+    I(n, :) = abs(E);    
+end   
+
+figure
+imagesc(z, x, rot90(I))
+colorbar
+title(sprintf("Beam radius = %.1f {\\mu}m. Glass start = %.1f {\\mu}m. Glass end = %.1f {\\mu}m. Medium parameter = %.3f", r, g_start, g_end, p))
+xlabel("z, mm")
+ylabel("x, mm")
+
+line([g_start g_start], [-Lx/2 Lx/2], 'Color','red','LineStyle','--');
+line([g_end g_end], [-Lx/2 Lx/2], 'Color','red','LineStyle','--');
+
+% colormap(gray)