def adjoint_solver(design_params, mon_type):
matgrid = mp.MaterialGrid(mp.Vector3(Nx,Ny),
mp.air,
silicon,
design_parameters=np.ones((Nx,Ny)))
matgrid_region = mpa.DesignRegion(matgrid,
volume=mp.Volume(center=mp.Vector3(),
size=mp.Vector3(design_shape.x,design_shape.y,0)))
matgrid_geometry = [mp.Block(center=matgrid_region.center,
size=matgrid_region.size,
material=matgrid)]
geometry = waveguide_geometry + matgrid_geometry
sim = mp.Simulation(resolution=resolution,
cell_size=cell_size,
boundary_layers=boundary_layers,
sources=sources,
geometry=geometry)
if mon_type.name == 'EIGENMODE':
obj_list = [mpa.EigenmodeCoefficient(sim,
mp.Volume(center=mp.Vector3(0.5*sxy-dpml),
size=mp.Vector3(0,sxy,0)),1)]
def J(mode_mon):
return npa.abs(mode_mon)**2
elif mon_type.name == 'DFT':
obj_list = [mpa.FourierFields(sim,
mp.Volume(center=mp.Vector3(0.5*sxy-dpml),
size=mp.Vector3(0,sxy,0)),
mp.Ez)]
def J(mode_mon):
return npa.abs(mode_mon[0,63])**2
opt = mpa.OptimizationProblem(
simulation = sim,
objective_functions = J,
objective_arguments = obj_list,
design_regions = [matgrid_region],
frequencies=[fcen],
decay_fields=[mp.Ez])
f, dJ_du = opt([design_params])
sim.reset_meep()
return f, dJ_du
def adjoint_solver_damping(design_params, frequencies=None, mat2=silicon):
matgrid = mp.MaterialGrid(mp.Vector3(Nx, Ny),
mp.air,
mat2,
weights=np.ones((Nx, Ny)),
damping=3.14 * fcen)
matgrid_region = mpa.DesignRegion(
matgrid,
volume=mp.Volume(center=mp.Vector3(),
size=mp.Vector3(design_region_size.x,
design_region_size.y, 0)))
matgrid_geometry = [
mp.Block(center=matgrid_region.center,
size=matgrid_region.size,
material=matgrid)
]
geometry = waveguide_geometry + matgrid_geometry
sim = mp.Simulation(resolution=resolution,
cell_size=cell_size,
boundary_layers=pml_xy,
sources=wvg_source,
geometry=geometry)
if not frequencies:
frequencies = [fcen]
obj_list = [
mpa.EigenmodeCoefficient(sim,
mp.Volume(
center=mp.Vector3(0.5 * sxy - dpml - 0.1),
size=mp.Vector3(0, sxy - 2 * dpml, 0)),
1,
eig_parity=eig_parity)
]
def J(mode_mon):
return npa.power(npa.abs(mode_mon), 2)
opt = mpa.OptimizationProblem(simulation=sim,
objective_functions=J,
objective_arguments=obj_list,
design_regions=[matgrid_region],
frequencies=frequencies,
minimum_run_time=150)
f, dJ_du = opt([design_params])
sim.reset_meep()
return f, dJ_du
def build_straight_wg_simulation(
wg_width=0.5,
wg_padding=1.0,
wg_length=1.0,
pml_width=1.0,
source_to_pml=0.5,
source_to_monitor=0.1,
frequencies=[1 / 1.55],
gaussian_rel_width=0.2,
sim_resolution=20,
design_region_resolution=20,
):
"""Builds a simulation of a straight waveguide with a design region segment."""
design_region_shape = (1.0, wg_width)
# Simulation domain size
sx = 2 * pml_width + 2 * wg_length + design_region_shape[0]
sy = 2 * pml_width + 2 * wg_padding + max(
wg_width,
design_region_shape[1],
)
# Mean / center frequency
fmean = onp.mean(frequencies)
si = mp.Medium(index=3.4)
sio2 = mp.Medium(index=1.44)
sources = [
mp.EigenModeSource(
mp.GaussianSource(frequency=fmean,
fwidth=fmean * gaussian_rel_width),
eig_band=1,
direction=mp.NO_DIRECTION,
eig_kpoint=mp.Vector3(1, 0, 0),
size=mp.Vector3(0, wg_width + 2 * wg_padding, 0),
center=[-sx / 2 + pml_width + source_to_pml, 0, 0],
),
mp.EigenModeSource(
mp.GaussianSource(frequency=fmean,
fwidth=fmean * gaussian_rel_width),
eig_band=1,
direction=mp.NO_DIRECTION,
eig_kpoint=mp.Vector3(-1, 0, 0),
size=mp.Vector3(0, wg_width + 2 * wg_padding, 0),
center=[sx / 2 - pml_width - source_to_pml, 0, 0],
),
]
nx, ny = int(design_region_shape[0] * design_region_resolution), int(
design_region_shape[1] * design_region_resolution)
mat_grid = mp.MaterialGrid(
mp.Vector3(nx, ny),
sio2,
si,
grid_type='U_DEFAULT',
)
design_regions = [
mpa.DesignRegion(
mat_grid,
volume=mp.Volume(
center=mp.Vector3(),
size=mp.Vector3(
design_region_shape[0],
design_region_shape[1],
0,
),
),
)
]
geometry = [
mp.Block(center=mp.Vector3(x=-design_region_shape[0] / 2 -
wg_length / 2 - pml_width / 2),
material=si,
size=mp.Vector3(wg_length + pml_width, wg_width,
0)), # left wg
mp.Block(center=mp.Vector3(x=+design_region_shape[0] / 2 +
wg_length / 2 + pml_width / 2),
material=si,
size=mp.Vector3(wg_length + pml_width, wg_width,
0)), # right wg
mp.Block(center=design_regions[0].center,
size=design_regions[0].size,
material=mat_grid), # design region
]
simulation = mp.Simulation(
cell_size=mp.Vector3(sx, sy),
boundary_layers=[mp.PML(pml_width)],
geometry=geometry,
sources=sources,
resolution=sim_resolution,
)
monitor_centers = [
mp.Vector3(-sx / 2 + pml_width + source_to_pml + source_to_monitor),
mp.Vector3(sx / 2 - pml_width - source_to_pml - source_to_monitor),
]
monitor_size = mp.Vector3(y=wg_width + 2 * wg_padding)
monitors = [
mpa.EigenmodeCoefficient(simulation,
mp.Volume(center=center, size=monitor_size),
mode=1,
forward=forward) for center in monitor_centers
for forward in [True, False]
]
return simulation, sources, monitors, design_regions, frequencies
mp.Block(center=design_region.center,
size=design_region.size,
material=design_variables,
e1=mp.Vector3(x=-1).rotate(mp.Vector3(z=1), np.pi / 2),
e2=mp.Vector3(y=1).rotate(mp.Vector3(z=1), np.pi / 2))
]
sim = mp.Simulation(cell_size=cell_size,
boundary_layers=pml_layers,
geometry=geometry,
sources=source,
eps_averaging=False,
resolution=resolution)
TE_top = mpa.EigenmodeCoefficient(sim,
mp.Volume(center=mp.Vector3(0, 1, 0),
size=mp.Vector3(x=2)),
mode=1)
ob_list = [TE_top]
def J(alpha):
return npa.abs(alpha)**2
opt = mpa.OptimizationProblem(simulation=sim,
objective_functions=J,
objective_arguments=ob_list,
design_regions=[design_region],
fcen=fcen,
df=0,
nf=1,
