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https://github.com/edoverg/MPID.git
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implemented new filtering system based on a Filter Class. Previously, filtering was made expensive by extreme padding, now this has been fixed by choosing a more appropriate padding size. The gradient chain based on unitcells has been implemented but the results have yet to be tested using FDTD, which will be the next step. Added some utilities to visualize the effect of filter radius on given input masks and added all data concerning unit cell simulations. Still to be done is to fix materials in the MEEP simulations, so as to account for true material behavior instead of relying on constant refractive indices.
This commit is contained in:
Edoardo Vergerio
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import meep as mp
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mp.verbosity(0)
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import numpy as np
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import matplotlib.pyplot as plt
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from mpi4py import MPI
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comm = MPI.COMM_WORLD
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rank = comm.Get_rank()
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size = comm.Get_size()
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resolution = 50 # pixels/unit length
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wvl_min = 1.5
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wvl_max = 1.6
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wvl_cen = 0.5*(wvl_min+wvl_max)
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fmin = 1/wvl_max
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fmax = 1/wvl_min
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fcen = 1/wvl_cen
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df = fmax-fmin
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nfreq = 20
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dpml = 1.0 #PML thickness
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dsub = 1.5 + wvl_cen #substrate thickness
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dpad = dsub #padding between cell and PML
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k_point = mp.Vector3(0,0,0) #used for PBC
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n_si = 3.45 #silicon refractive index
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si = mp.Medium(index=n_si)
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n_sio2 = 1.45
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sio2 = mp.Medium(index=n_sio2)
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n_air = 1.0 #air refractive index
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air = mp.Medium(index=n_air)
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P = 0.7 #unit cell pitch
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h = 0.9 #pillar height
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def unitCell_paramsweep(D):
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print("Rank {}: Running simulation for diameter {}".format(rank, D))
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sim_x_size = dpml + dsub + dpad + dpml
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sim_z_size = P
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sim_y_size = P
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cell_size = mp.Vector3(sim_x_size, sim_y_size, sim_z_size)
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source_position = mp.Vector3(-wvl_cen,0,0) #source position in the middle of the substrate
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source = mp.Source(
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mp.GaussianSource(fcen, fwidth=df),
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component = mp.Ez,
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center = source_position,
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size = mp.Vector3(0, sim_y_size, sim_z_size),
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)
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pml_layers = [mp.PML(dpml,direction=mp.X)]
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monitor_position = mp.Vector3(h + wvl_cen,0,0)
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obs_point = monitor_position
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stop_cond = mp.stop_when_fields_decayed(50, mp.Ez, obs_point, 1e-9)
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#stop_cond = 10
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sim = mp.Simulation(
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resolution = resolution,
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cell_size = cell_size,
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boundary_layers = pml_layers,
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k_point = k_point,
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default_material = sio2,
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sources = [source],
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)
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flux_mon = sim.add_flux(
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fcen,
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df,
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nfreq,
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mp.FluxRegion(center=monitor_position, size=mp.Vector3(0, sim_y_size, sim_z_size))
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)
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sim.run(until_after_sources=stop_cond)
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input_flux = mp.get_fluxes(flux_mon)
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sim.reset_meep()
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pillar_geo = mp.Cylinder(
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material = si,
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radius = D/2,
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height = h,
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center = mp.Vector3(h/2,0,0),
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axis=mp.Vector3(1,0,0),
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)
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substrate_geo = mp.Block(
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material = sio2,
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size = mp.Vector3(dsub+dpml, mp.inf, mp.inf),
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center = mp.Vector3(-(dsub+dpml)/2,0,0),
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)
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geometries = [substrate_geo, pillar_geo]
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sim = mp.Simulation(
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resolution = resolution,
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cell_size = cell_size,
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boundary_layers = pml_layers,
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geometry = geometries,
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k_point = k_point,
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sources = [source],
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)
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mode_mon = sim.add_flux(
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fcen, df, nfreq, mp.FluxRegion(center=monitor_position, size=mp.Vector3(0, sim_y_size, sim_z_size))
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)
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sim.run(until_after_sources=stop_cond)
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freqs = mp.get_eigenmode_freqs(mode_mon)
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res = sim.get_eigenmode_coefficients(
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mode_mon, [1], eig_parity=mp.ODD_Z + mp.EVEN_Y
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)
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coeffs = res.alpha
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mode_wvl = [1/freqs[nf] for nf in range(nfreq)]
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mode_tran = [abs(coeffs[0,nf,0])**2 / input_flux[nf] for nf in range(nfreq)]
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mode_phase = [np.angle(coeffs[0,nf,0]) for nf in range(nfreq)]
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return mode_wvl, mode_tran, mode_phase
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if rank == 0:
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diameters = np.linspace(0.1, 0.6, 24)
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else:
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diameters = None
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diameters = comm.bcast(diameters, root=0)
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local_diameters = np.array_split(diameters, size)[rank]
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local_indices = np.array_split(np.arange(len(diameters)), size)[rank]
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local_mode_tran_arr = np.zeros((len(diameters), nfreq))
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local_mode_phase_arr = np.zeros((len(diameters), nfreq))
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for local_i, (global_i, D) in enumerate(zip(local_indices,local_diameters)):
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mode_wvl, mode_tran, mode_phase = unitCell_paramsweep(D)
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local_mode_tran_arr[global_i,:] = mode_tran
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local_mode_phase_arr[global_i,:] = mode_phase
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mode_tran_arr = comm.gather(local_mode_tran_arr, root=0)
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mode_phase_arr = comm.gather(local_mode_phase_arr, root=0)
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if rank == 0:
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final_mode_tran_arr = np.zeros((len(diameters), nfreq))
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final_mode_phase_arr = np.zeros((len(diameters), nfreq))
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num_diameters_per_rank = len(diameters) // size
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for i in range(0, size):
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for j in range(num_diameters_per_rank):
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global_index = i * num_diameters_per_rank + j
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final_mode_tran_arr[global_index, :] = mode_tran_arr[i][global_index, :]
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final_mode_phase_arr[global_index, :] = mode_phase_arr[i][global_index, :]
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np.save("unit_cell_param_sweep_diameters.npy", diameters)
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np.save("unit_cell_param_sweep_mode_wvl.npy", mode_wvl)
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np.save("unit_cell_param_sweep_mode_tran.npy", final_mode_tran_arr)
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np.save("unit_cell_param_sweep_mode_phase.npy", final_mode_phase_arr)
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plt.figure()
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plt.subplot(1,2,1)
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plt.pcolormesh(
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mode_wvl,
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diameters,
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final_mode_tran_arr,
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cmap='hot_r',
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shading='gouraud',
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vmin=0,
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vmax=final_mode_tran_arr.max(),
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)
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plt.axis([wvl_min, wvl_max, diameters[0], diameters[-1]])
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plt.xlabel("Wavelength (um)")
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plt.xticks([t for t in np.linspace(wvl_min, wvl_max, 3)])
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plt.ylabel("Pillar Diameter (um)")
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plt.title("Transmission")
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cbar=plt.colorbar()
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cbar.set_ticks([t for t in np.arange(0, 1.2, 0.2)])
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plt.subplot(1,2,2)
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plt.pcolormesh(
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mode_wvl,
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diameters,
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final_mode_phase_arr,
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cmap='RdBu',
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shading='gouraud',
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vmin=final_mode_phase_arr.min(),
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vmax=final_mode_phase_arr.max(),
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)
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plt.axis([wvl_min, wvl_max, diameters[0], diameters[-1]])
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plt.xlabel("Wavelength (um)")
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plt.xticks([t for t in np.linspace(wvl_min, wvl_max, 3)])
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plt.ylabel("Pillar Diameter (um)")
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plt.title("phase")
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cbar=plt.colorbar()
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cbar.set_ticks([t for t in np.arange(-3, 4, 1)])
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plt.subplots_adjust(wspace=0.5)
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plt.savefig("unit_cell_param_sweep.pdf")
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