MATLAB Code for Calculating Waveguide Fields at Fundamental and Double Fundamental Frequencies

Sure! Here's a code snippet in MATLAB that calculates the whole fields of the waveguide and its outside air at the fundamental frequency and at the double fundamental frequency:
\n```matlab
% Constants
c = 3e8; % Speed of light in vacuum (m/s)
f0 = 8e12; % Fundamental frequency (Hz)
f2f0 = 2f0; % Double fundamental frequency (Hz)
lambda0 = c/f0; % Wavelength at fundamental frequency (m)
lambda2f0 = c/f2f0; % Wavelength at double fundamental frequency (m)
w = 4e-6; % Width of the ZnO waveguide (m)

% Spatial grid
dz = lambda0/10; % Step size along z-axis (m)
z = -10lambda0:dz:10lambda0; % Range along z-axis (m)
dy = 1e-6; % Step size along y-axis (m)
y = -10w:dy:10w; % Range along y-axis (m)

% Electric field at the fundamental frequency
E_fundamental = exp(1i2pif0z/c);

% Electric field at the double fundamental frequency
E_double_fundamental = exp(1i2pif2f0*z/c);

% Plotting the fields
figure;
subplot(2,1,1);
imagesc(z, y, real(E_fundamental));
xlabel('z (m)');
ylabel('y (m)');
title('Electric Field at Fundamental Frequency');
colorbar;

subplot(2,1,2);
imagesc(z, y, real(E_double_fundamental));
xlabel('z (m)');
ylabel('y (m)');
title('Electric Field at Double Fundamental Frequency');
colorbar;\

\
Note: This code assumes that you have already installed and set up MATLAB on your computer. Additionally, this code only calculates and visualizes the electric field along the z-axis (propagation direction) and y-axis (invariant direction) in the waveguide and its outside air. If you need to consider other aspects or perform further calculations, you may need to modify the code accordingly.