## launch a Gaussian beam

import meep as mp
import math
import matplotlib
matplotlib.use('agg')
import matplotlib.pyplot as plt

s = 14
resolution = 50
dpml = 2

cell_size = mp.Vector3(s,s)

boundary_layers = [mp.PML(thickness=dpml)]

beam_x0 = mp.Vector3(0,3.0)    # beam focus (relative to source center)
rot_angle = 0  # CCW rotation angle about z axis (0: +y axis)
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)
fcen = 1
sources = [mp.GaussianBeamSource(src=mp.ContinuousSource(fcen),
                                 center=mp.Vector3(0,-0.5*s+dpml+1.0),
                                 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)

sim.run(until=20)

sim.plot2D(fields=mp.Ez,
           output_plane=mp.Volume(center=mp.Vector3(),
                                  size=mp.Vector3(s-2*dpml,s-2*dpml)))

plt.savefig('Ez_angle{}.png'.format(rot_angle),bbox_inches='tight',pad_inches=0)