6. Vector Fast Fourier Transform (VFFT)

The incident field is an vector field (Ex, Ey) and it is propagated and converted to (Ex,Ey,Ez)

from diffractio import np, sp, plt
from diffractio import nm, um, mm, degrees

from diffractio.scalar_masks_XY import Scalar_mask_XY
from diffractio.scalar_fields_XY import Scalar_field_XY
from diffractio.scalar_sources_XY import Scalar_source_XY

from diffractio.vector_fields_XY import Vector_field_XY
from diffractio.vector_sources_XY import Vector_source_XY
from diffractio.vector_masks_XY import Vector_mask_XY

6.1. XY scheme

size = 64 * um
x0 = np.linspace(-size / 2, size / 2, 1024)
y0 = np.linspace(-size / 2, size / 2, 1024)

wavelength = 0.6328 * um

u0 = Scalar_source_XY(x0, y0, wavelength)
u0.gauss_beam(r0=(0, 0),
              w0=(16 * um, 16 * um),
              z0=0 * um,
              A=1,
              theta=0. * degrees,
              phi=0 * degrees)

u0.draw()

radius = 8 * um
t = Scalar_mask_XY(x0, y0, wavelength)
t.circle(r0=(0, 0), radius=radius)

u1 = t * u0

EM1 = Vector_source_XY(x0, y0, wavelength)
EM1.constant_polarization(u=u1, v=(1, 0))

EM1.draw(kind='ellipses',
         amplification=0.5,
         color_line='k',
         line_width=0.75,
         num_ellipses=(21, 21))

EM2 = EM1.VFFT(radius=64 * um,
               focal=10 * um,
               remove0=False,
               n=1,
               new_field=True,
               has_draw=False)

x_resample = 8
EM2.cut_resample([-x_resample, x_resample], [-x_resample, x_resample],
                 num_points=(1024, 1024))

EM2.draw('intensities', logarithm=1e-1)

EM2.draw('intensity', logarithm=1e-1)

This result can be compared to the scalar FFT result.

u_fft = u1.fft(z=15 * um, new_field=True, remove0=False)
u_fft.cut_resample(x_limits=(-x_resample, x_resample),
                   y_limits=(-x_resample, x_resample))
u_fft.draw(logarithm=1e-2, has_colorbar='horizontal')