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## linear-chirped pulse planewave with higher frequencies at the front (down-chirp)
import numpy as np
import meep as mp
resolution = 40
dpml = 2
pml_layers = [mp.PML(thickness=dpml, direction=mp.X)]
sx = 40
sy = 6
cell_size = mp.Vector3(sx + 2 * dpml, sy)
v0 = 1.0 # pulse center frequency
a = 0.2 # Gaussian envelope half-width
b = -0.5 # linear chirp rate (positive: up-chirp, negative: down-chirp)
t0 = 15 # peak time
chirp = lambda t: np.exp(1j * 2 * np.pi * v0 * (t - t0)) * np.exp(
-a * (t - t0) ** 2 + 1j * b * (t - t0) ** 2
)
sources = [
mp.Source(
src=mp.CustomSource(src_func=chirp),
center=mp.Vector3(-0.5 * sx),
size=mp.Vector3(y=sy),
component=mp.Ez,
)
]
sim = mp.Simulation(
cell_size=cell_size,
boundary_layers=pml_layers,
resolution=resolution,
k_point=mp.Vector3(),
sources=sources,
symmetries=[mp.Mirror(mp.Y)],
)
sim.run(
mp.in_volume(
mp.Volume(center=mp.Vector3(), size=mp.Vector3(sx, sy)),
mp.at_every(2.7, mp.output_efield_z),
),
until=t0 + 50,
)
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