Two-dimensional Fast Fourier Transforms (FFT) of four-wave mixing

Two-dimensional Fast Fourier Transforms (FFT) of four-wave mixing, at $\omega t% = 1, 100 and 200, used to create Fig.5. The FFTs are created out of OSIRIS electric field data using numpy:

np.log10(np.abs((fftshift(fftn(dataset_e3)))))

The 2D slices are taken at $k_z$ = 0, and are 2D arrays whose first axis corresponds to $k_y$ and second corresponds to $k_x$. To convert from the array index to k/k_0 value, do (index - 875) / 56. 875 is half of the number of grid points or indices along one axis (since k=0 starts from the middle), and 56 the index of k_0.