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from __future__ import division
import unittest
import meep as mp
import math
import numpy as np
class TestGaussianBeamSource(unittest.TestCase):
def gaussian_beam(self, rot_angle):
s = 14
resolution = 25
dpml = 2
cell_size = mp.Vector3(s,s)
boundary_layers = [mp.PML(thickness=dpml)]
beam_x0 = mp.Vector3(0,7.0) # beam focus (relative to source center)
beam_kdir = mp.Vector3(0,1,0).rotate(mp.Vector3(0,0,1),math.radians(rot_angle)) # beam propagation direction
beam_w0 = 0.8 # beam waist radius
beam_E0 = mp.Vector3(0,0,1)
beam_x0 = beam_x0.rotate(mp.Vector3(0,0,1),math.radians(rot_angle))
fcen = 1
src_x = 0
src_y = -0.5*s+dpml+1.0
sources = [mp.GaussianBeamSource(src=mp.GaussianSource(fcen,fwidth=0.2*fcen),
center=mp.Vector3(src_x,src_y),
size=mp.Vector3(s),
beam_x0=beam_x0,
beam_kdir=beam_kdir,
beam_w0=beam_w0,
beam_E0=beam_E0)]
sim = mp.Simulation(resolution=resolution,
cell_size=cell_size,
boundary_layers=boundary_layers,
sources=sources)
cell_dft_fields = sim.add_dft_fields([mp.Ez], fcen, 0, 1, center=mp.Vector3(), size=mp.Vector3(s-2*dpml,s-2*dpml))
sim.run(until_after_sources=50)
Ez_cell = sim.get_dft_array(cell_dft_fields, mp.Ez, 0)
[x,y,z,w] = sim.get_array_metadata(dft_cell=cell_dft_fields)
tol = 0.05
idx_x = np.nonzero((np.squeeze(x) > (src_x+beam_x0.x-tol)) & (np.squeeze(x) < (src_x+beam_x0.x+tol)))
idx_y = np.nonzero((np.squeeze(y) > (src_y+beam_x0.y-tol)) & (np.squeeze(y) < (src_y+beam_x0.y+tol)))
Ez_beam_x0 = Ez_cell[np.squeeze(idx_x)[0],np.squeeze(idx_y)[0]]
frac = np.abs(Ez_beam_x0)**2 / np.amax(np.abs(Ez_cell)**2)
print("ratio of the Gaussian beam energy at the focus over the maximum beam energy for the entire cell: {}".format(frac))
self.assertGreater(frac, 0.99)
def test_gaussian_beam(self):
self.gaussian_beam(-40)
if __name__ == '__main__':
unittest.main()
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