PN Junction Modulator

Note: The device designs presented here are intended as proof-of-concept examples to illustrate workflows, modeling approaches, and design methodology. Performance metrics are not optimized, and the structures are not intended for tape-out.

Source Code

# Import the necassry packages
import gplugins.modes as gm
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
import meep as mp
import gdsfactory as gf
# from ubcpdk import PDK, cells
# from functools import partial
# PDK.activate()
import sax
from jax import config
config.update("jax_enable_x64", True)
import jax.numpy as jnp
from simphony.libraries import siepic
from gplugins.devsim import get_simulation_xsection
from gplugins.devsim.get_simulation_xsection import k_to_alpha, clear_devsim_cache
import pyvista as pv
import os

Using MPI version 4.1, 1 processes
2025-11-26 06:39:24.584 | INFO     | gplugins.gmeep:<module>:39 - Meep '1.31.0' installed at ['/home/ramprakash/anaconda3/envs/si_photo/lib/python3.13/site-packages/meep']
Searching DEVSIM_MATH_LIBS="libopenblas.so:liblapack.so:libblas.so"
Loading "libopenblas.so": ALL BLAS/LAPACK LOADED
Skipping liblapack.so
Skipping libblas.so
loading UMFPACK 5.1 as direct solver
2025-11-26 06:39:27.467 | INFO     | gplugins.devsim:<module>:16 - DEVSIM '2.10.0' installed at ['/home/ramprakash/anaconda3/envs/si_photo/lib/python3.13/site-packages/devsim']

Design of PN junction

Loading a straing pn junciton component from gdsfactory

The aim is to do full TCAD simulation to get the Vpi

Step 1: Import PN junction straight waveguide form GDSFactory

Source Code

import gdsfactory as gf
from gdsfactory.generic_tech import LAYER, LAYER_STACK
from gdsfactory.technology import LayerLevel, LayerStack

# We choose a representative subdomain of the component
waveguide = gf.Component()
waveguide.add_ref(
    gf.functions.trim(
        component=gf.components.straight_pn(length=10, taper=None).copy(),
        domain=[[3, -4], [3, 4], [5, 4], [5, -4]],
    )
)

waveguide.plot()

scene = waveguide.to_3d()
scene.show()

Run a TCAD simualtion to calculate the carrier desnity of electron (dN) and holes (dP)

Source Code

active_layer_stack = gf.pdk.get_active_pdk().layer_stack
active_layer_stack.layers

{'substrate': LayerLevel(name=None, layer=WAFER, derived_layer=None, thickness=10.0, thickness_tolerance=None, width_tolerance=None, zmin=-13.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=101, material='si', info={}),
 'box': LayerLevel(name=None, layer=WAFER, derived_layer=None, thickness=3.0, thickness_tolerance=None, width_tolerance=None, zmin=-3.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=9, material='sio2', info={}),
 'core': LayerLevel(name=None, layer=((WG - DEEP_ETCH) - SHALLOW_ETCH), derived_layer=WG, thickness=0.22, thickness_tolerance=None, width_tolerance=None, zmin=0.0, zmin_tolerance=None, sidewall_angle=10.0, sidewall_angle_tolerance=None, width_to_z=0.5, z_to_bias=None, bias=None, mesh_order=2, material='si', info={}),
 'shallow_etch': LayerLevel(name=None, layer=(SHALLOW_ETCH & WG), derived_layer=SLAB150, thickness=0.07, thickness_tolerance=None, width_tolerance=None, zmin=0.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=1, material='si', info={}),
 'deep_etch': LayerLevel(name=None, layer=DEEP_ETCH, derived_layer=SLAB90, thickness=0.13, thickness_tolerance=None, width_tolerance=None, zmin=0.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=1, material='si', info={}),
 'clad': LayerLevel(name=None, layer=WAFER, derived_layer=None, thickness=3.0, thickness_tolerance=None, width_tolerance=None, zmin=0.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=10, material='sio2', info={}),
 'slab150': LayerLevel(name=None, layer=SLAB150, derived_layer=None, thickness=0.15, thickness_tolerance=None, width_tolerance=None, zmin=0.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=3, material='si', info={}),
 'slab90': LayerLevel(name=None, layer=SLAB90, derived_layer=None, thickness=0.09, thickness_tolerance=None, width_tolerance=None, zmin=0.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=2, material='si', info={}),
 'nitride': LayerLevel(name=None, layer=WGN, derived_layer=None, thickness=0.35000000000000003, thickness_tolerance=None, width_tolerance=None, zmin=0.32, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=2, material='sin', info={}),
 'ge': LayerLevel(name=None, layer=GE, derived_layer=None, thickness=0.5, thickness_tolerance=None, width_tolerance=None, zmin=0.22, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=1, material='ge', info={}),
 'undercut': LayerLevel(name=None, layer=UNDERCUT, derived_layer=None, thickness=-5.0, thickness_tolerance=None, width_tolerance=None, zmin=-3.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=([0.0, 0.3, 0.6, 0.8, 0.9, 1.0], [0.0, -0.5, -1.0, -1.5, -2.0, -2.5]), bias=None, mesh_order=1, material='air', info={}),
 'via_contact': LayerLevel(name=None, layer=VIAC, derived_layer=None, thickness=1.01, thickness_tolerance=None, width_tolerance=None, zmin=0.09, zmin_tolerance=None, sidewall_angle=-10.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=1, material='Aluminum', info={}),
 'metal1': LayerLevel(name=None, layer=M1, derived_layer=None, thickness=0.7000000000000001, thickness_tolerance=None, width_tolerance=None, zmin=1.1, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=2, material='Aluminum', info={}),
 'heater': LayerLevel(name=None, layer=HEATER, derived_layer=None, thickness=0.75, thickness_tolerance=None, width_tolerance=None, zmin=1.1, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=2, material='TiN', info={}),
 'via1': LayerLevel(name=None, layer=VIA1, derived_layer=None, thickness=0.49999999999999956, thickness_tolerance=None, width_tolerance=None, zmin=1.8000000000000003, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=1, material='Aluminum', info={}),
 'metal2': LayerLevel(name=None, layer=M2, derived_layer=None, thickness=0.7000000000000001, thickness_tolerance=None, width_tolerance=None, zmin=2.3, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=2, material='Aluminum', info={}),
 'via2': LayerLevel(name=None, layer=VIA2, derived_layer=None, thickness=0.20000000000000018, thickness_tolerance=None, width_tolerance=None, zmin=3.0, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=1, material='Aluminum', info={}),
 'metal3': LayerLevel(name=None, layer=M3, derived_layer=None, thickness=2.0, thickness_tolerance=None, width_tolerance=None, zmin=3.2, zmin_tolerance=None, sidewall_angle=0.0, sidewall_angle_tolerance=None, width_to_z=0.0, z_to_bias=None, bias=None, mesh_order=2, material='Aluminum', info={})}

Simple step doping. See below for complex doping profile

Source Code

%%capture  
um = 1e-6
c = get_simulation_xsection.PINWaveguide(
    core_width=0.500 * um,
    core_thickness=0.220 * um,
    slab_thickness=0.090 * um,
)
# Initialize mesh and solver
clear_devsim_cache()
c.ddsolver()
c.save_device('straight_PN.dat')

Source Code

c.plot(scalars="Holes", log_scale=True, jupyter_backend="static")

2025-11-25 20:17:21.123 (5189.345s) [    7BAE26EE4740]vtkXOpenGLRenderWindow.:1458  WARN| bad X server connection. DISPLAY=

Source Code

c.list_fields()

Header

Data Arrays

UnstructuredGrid Information N Cells 8424 N Points 4401 X Bounds -2.478e-05, 2.511e-05 Y Bounds 9.000e-06, 2.200e-05 Z Bounds 0.000e+00, 0.000e+00 N Arrays 99

Name Field Type N Comp Min Max Acceptors Points float32 1 0.000e+00 1.000e+17 AtContactNode Points float32 1 0.000e+00 0.000e+00 ContactNSurfaceNormal_x Points float32 1 0.000e+00 0.000e+00 ContactNSurfaceNormal_y Points float32 1 0.000e+00 0.000e+00 ContactSurfaceArea Points float32 1 0.000e+00 0.000e+00 Donors Points float32 1 0.000e+00 1.000e+17 ElectronGeneration Points float32 1 3.146e-26 1.285e-19 ElectronGeneration:Electrons Points float32 1 -1.600e-14 -1.600e-28 ElectronGeneration:Holes Points float32 1 -1.600e-14 -1.600e-28 Electrons Points float32 1 1.000e+03 1.000e+17 Electrons_prev Points float32 1 1.000e+10 1.000e+10 HoleGeneration Points float32 1 -1.285e-19 -3.146e-26 HoleGeneration:Electrons Points float32 1 1.600e-28 1.600e-14 HoleGeneration:Holes Points float32 1 1.600e-28 1.600e-14 Holes Points float32 1 1.000e+03 1.000e+17 Holes_prev Points float32 1 1.000e+10 1.000e+10 IntrinsicCharge Points float32 1 -1.000e+17 1.000e+17 IntrinsicCharge:Potential Points float32 1 -3.863e+18 -7.736e+11 IntrinsicElectrons Points float32 1 1.000e+03 1.000e+17 IntrinsicElectrons:Potential Points float32 1 3.863e+04 3.863e+18 IntrinsicHoles Points float32 1 1.000e+03 1.000e+17 IntrinsicHoles:Potential Points float32 1 -3.863e+18 -3.863e+04 NCharge Points float32 1 -1.600e-02 -1.600e-16 NCharge:Electrons Points float32 1 -1.600e-19 -1.600e-19 NSurfaceNormal_x Points float32 1 0.000e+00 0.000e+00 NSurfaceNormal_y Points float32 1 -1.000e+00 0.000e+00 NetDoping Points float32 1 -1.000e+17 1.000e+17 NodeVolume Points float32 1 7.631e-15 6.522e-13 PCharge Points float32 1 1.600e-16 1.600e-02 PCharge:Holes Points float32 1 1.600e-19 1.600e-19 Potential Points float32 1 -4.173e-01 4.173e-01 PotentialIntrinsicCharge Points float32 1 -1.600e-02 1.600e-02 PotentialIntrinsicCharge:Potential Points float32 1 1.238e-07 6.181e-01 PotentialNodeCharge Points float32 1 -1.600e-02 1.600e-02 PotentialNodeCharge:Electrons Points float32 1 1.600e-19 1.600e-19 PotentialNodeCharge:Holes Points float32 1 -1.600e-19 -1.600e-19 Potential_prev Points float32 1 0.000e+00 0.000e+00 SurfaceArea Points float32 1 0.000e+00 6.856e-07 USRH Points float32 1 -8.034e-01 -1.966e-07 USRH:Electrons Points float32 1 1.000e-09 1.000e+05 USRH:Holes Points float32 1 1.000e-09 1.000e+05 coordinate_index Points float32 1 5.148e+03 1.246e+04 leftnodeelectrons Points float32 1 0.000e+00 0.000e+00 leftnodeelectrons:Electrons Points float32 1 0.000e+00 0.000e+00 leftnodeholes Points float32 1 0.000e+00 0.000e+00 leftnodeholes:Holes Points float32 1 0.000e+00 0.000e+00 leftnodemodel Points float32 1 0.000e+00 0.000e+00 leftnodemodel:Potential Points float32 1 0.000e+00 0.000e+00 node_index Points float32 1 0.000e+00 4.400e+03 rightnodeelectrons Points float32 1 0.000e+00 0.000e+00 rightnodeelectrons:Electrons Points float32 1 0.000e+00 0.000e+00 rightnodeholes Points float32 1 0.000e+00 0.000e+00 rightnodeholes:Holes Points float32 1 0.000e+00 0.000e+00 rightnodemodel Points float32 1 0.000e+00 0.000e+00 rightnodemodel:Potential Points float32 1 0.000e+00 0.000e+00 Bern01 Points float32 1 1.000e+00 1.187e+00 Bern01:Potential@n0 Points float32 1 -2.368e+01 -1.660e+01 Bern01:Potential@n1 Points float32 1 1.660e+01 2.368e+01 EdgeCouple Points float32 1 6.908e-08 5.446e-07 EdgeInverseLength Points float32 1 1.101e+06 9.710e+06 EdgeLength Points float32 1 1.399e-07 9.389e-07 EdgeNodeVolume Points float32 1 1.908e-15 1.087e-13 ElectricField Points float32 1 -6.838e+04 -2.951e-04 ElectricField:Potential@n0 Points float32 1 1.101e+06 9.710e+06 ElectricField:Potential@n1 Points float32 1 -9.710e+06 -1.101e+06 ElectronCurrent Points float32 1 -3.719e-10 3.361e-10 ElectronCurrent:Electrons@n0 Points float32 1 -1.822e-11 -1.824e-12 ElectronCurrent:Electrons@n1 Points float32 1 1.824e-12 1.417e-11 ElectronCurrent:Holes@n0 Points float32 1 0.000e+00 0.000e+00 ElectronCurrent:Holes@n1 Points float32 1 0.000e+00 0.000e+00 ElectronCurrent:Potential@n0 Points float32 1 7.077e-08 2.070e+07 ElectronCurrent:Potential@n1 Points float32 1 -2.070e+07 -7.077e-08 Electrons@n0 Points float32 1 1.000e+03 1.000e+17 Electrons@n1 Points float32 1 1.000e+03 1.000e+17 HoleCurrent Points float32 1 -1.647e-10 4.010e-10 HoleCurrent:Electrons@n0 Points float32 1 0.000e+00 0.000e+00 HoleCurrent:Electrons@n1 Points float32 1 0.000e+00 0.000e+00 HoleCurrent:Holes@n0 Points float32 1 9.121e-13 7.085e-12 HoleCurrent:Holes@n1 Points float32 1 -9.110e-12 -9.121e-13 HoleCurrent:Potential@n0 Points float32 1 3.523e-08 1.036e+07 HoleCurrent:Potential@n1 Points float32 1 -1.036e+07 -3.523e-08 Holes@n0 Points float32 1 1.000e+03 1.000e+17 Holes@n1 Points float32 1 1.000e+03 1.000e+17 Potential@n0 Points float32 1 -4.173e-01 4.173e-01 Potential@n1 Points float32 1 -4.173e-01 4.173e-01 PotentialEdgeFlux Points float32 1 -6.717e-08 -2.899e-16 PotentialEdgeFlux:Potential@n0 Points float32 1 1.082e-06 9.539e-06 PotentialEdgeFlux:Potential@n1 Points float32 1 -9.539e-06 -1.082e-06 contactcharge_edge Points float32 1 0.000e+00 0.000e+00 contactcharge_edge:Potential@n0 Points float32 1 0.000e+00 0.000e+00 contactcharge_edge:Potential@n1 Points float32 1 0.000e+00 0.000e+00 edge_index Points float32 1 5.000e-01 1.281e+04 unitx Points float32 1 1.104e-02 7.402e-01 unity Points float32 1 3.912e-04 7.012e-01 vdiff Points float32 1 -3.476e-01 -1.097e-12 vdiff:Potential@n0 Points float32 1 3.863e+01 3.863e+01 vdiff:Potential@n1 Points float32 1 -3.863e+01 -3.863e+01 ElementEdgeCouple Cells float32 1 4.210e-08 2.739e-07 ElementNodeVolume Cells float32 1 8.770e-16 5.506e-14

Source Code

mesh = pv.read('straight_PN.dat')
fields = [
    "NetDoping","Donors","Acceptors",
    "Electrons","Holes"]

p = pv.Plotter(shape=(3,2), notebook='static', window_size=(320*4, 240*4))
# c.plot(scalars="NetDoping", jupyter_backend="static")

idx = 0
for r in range(3):
    for ccol in range(2):
        p.subplot(r, ccol)

        if idx >= len(fields):
            p.add_text("")  # empty cell
            continue

        fname = fields[idx]
        idx += 1

        # if fname not in mesh.array_names:
        #     p.add_text(f"Missing {fname}")
        #     continue

        p.add_mesh(mesh, scalars=fname, cmap="RdBu")
        p.add_text(fname, position="upper_edge", font_size=12)
        _ = p.camera_position = "xy"
        p.add_scalar_bar(title=fname)

p.link_views()
p.show()

/home/ramprakash/anaconda3/envs/si_photo/lib/python3.13/site-packages/pyvista/jupyter/notebook.py:56: UserWarning: Failed to use notebook backend: 

No module named 'trame'

Falling back to a static output.
  warnings.warn(

Applying voltage and finding the solution

Source Code

%%capture
# Find a solution with 1V across the junction, ramping by 0.1V steps
c.ramp_voltage(Vfinal=1, Vstep=0.1)
c.save_device('straight_PN_1V.dat')

Source Code

mesh = pv.read('straight_PN_1V.dat')
fields = [
    "NetDoping","Donors","Acceptors",
    "Electrons","Holes"]

p = pv.Plotter(shape=(3,2), notebook='static', window_size=(320*4, 240*4))
# c.plot(scalars="NetDoping", jupyter_backend="static")

idx = 0
for r in range(3):
    for ccol in range(2):
        p.subplot(r, ccol)

        if idx >= len(fields):
            p.add_text("")  # empty cell
            continue

        fname = fields[idx]
        idx += 1

        # if fname not in mesh.array_names:
        #     p.add_text(f"Missing {fname}")
        #     continue

        p.add_mesh(mesh, scalars=fname, cmap="RdBu")
        p.add_text(fname, position="upper_edge", font_size=12)
        _ = p.camera_position = "xy"
        p.add_scalar_bar(title=fname)

p.link_views()
p.show()

/home/ramprakash/anaconda3/envs/si_photo/lib/python3.13/site-packages/pyvista/jupyter/notebook.py:56: UserWarning: Failed to use notebook backend: 

No module named 'trame'

Falling back to a static output.
  warnings.warn(

Negative bias -1V

Source Code

%%capture
# Find a solution with 1V across the junction, ramping by 0.1V steps
c.ramp_voltage(Vfinal=-1, Vstep=-0.1)
c.save_device('straight_PN_-1V.dat')

Source Code

mesh = pv.read('straight_PN_-1V.dat')
fields = [
    "NetDoping","Donors","Acceptors",
    "Electrons","Holes"]

p = pv.Plotter(shape=(3,2), notebook='static', window_size=(320*4, 240*4))
# c.plot(scalars="NetDoping", jupyter_backend="static")

idx = 0
for r in range(3):
    for ccol in range(2):
        p.subplot(r, ccol)

        if idx >= len(fields):
            p.add_text("")  # empty cell
            continue

        fname = fields[idx]
        idx += 1

        # if fname not in mesh.array_names:
        #     p.add_text(f"Missing {fname}")
        #     continue

        p.add_mesh(mesh, scalars=fname, cmap="RdBu")
        p.add_text(fname, position="upper_edge", font_size=12)
        _ = p.camera_position = "xy"
        p.add_scalar_bar(title=fname)

p.link_views()
p.show()

/home/ramprakash/anaconda3/envs/si_photo/lib/python3.13/site-packages/pyvista/jupyter/notebook.py:56: UserWarning: Failed to use notebook backend: 

No module named 'trame'

Falling back to a static output.
  warnings.warn(

Source Code

def plot_carriers(label):
    x  = c.get_field("core", "x")
    Ne = c.get_field("core", "Electrons")
    Ph = c.get_field("core", "Holes")

    idx = np.argsort(x)
    plt.semilogy(x, Ne, label=f"Ne {label}")
    plt.semilogy(x, Ph, label=f"Ph {label}")
    plt.legend()

clear_devsim_cache()
c.ddsolver()
plot_carriers("0V")

clear_devsim_cache()
c.ddsolver()
c.ramp_voltage(Vfinal=-1, Vstep=-0.1)
plot_carriers("-1 V")

clear_devsim_cache()
c.ddsolver()
c.ramp_voltage(Vfinal=1, Vstep=0.1)
plot_carriers("+1 V")

Making waveguide from the devsim device with perturebd index and calculaitng the effective index. Using tidy3d for the mode calcaultions

Source Code

%%capture

voltages = [0, -0.2, -0.4, -0.6, -0.8, -1,-1.5, -2,-2.5, -3]#-0.5, -1, -1.5, -2, -2.5, -3, -3.5, -4]
ramp_step = -0.1 

n_dist = {}
neffs   = {}

clear_devsim_cache()
c.ddsolver()     # fresh, clean equilibrium state
cached = "/home/ramprakash/.gdsfactory/modes/Waveguide_*.npz"
if os.path.exists(cached):
    os.remove(cached)
current_bias = 0.0   # solved at 0 V


for ind, voltage in enumerate(voltages):
    clear_devsim_cache()
    c.ddsolver()
    c.ramp_voltage(Vfinal=voltage, Vstep=ramp_step)
    waveguide = c.make_waveguide(wavelength=1.55, perturb=True, grid_resolution=20)
    n_dist[voltage] = waveguide.index.values
    neffs[voltage] = waveguide.n_eff[0]

# for V in voltages:
#     # Skip ramp if already at this voltage
#     if V != current_bias:
#         # choose step direction automatically
#         step = ramp_step if V < current_bias else abs(ramp_step)
#         # ramp from current bias → new voltage
#         c.ramp_voltage(Vfinal=V, Vstep=step, Vinit=current_bias)

#     current_bias = V
    
#     # build perturbed optical waveguide - Smaller res for faster run
#     wg = c.make_waveguide(wavelength=1.55, perturb=True)

#     n_dist[V] = wg.index.values
#     # neffs[V] = wg.n_eff[0]
#     print(f"Voltage value: {V}")

Source Code

%%capture
clear_devsim_cache()
c.ddsolver()     # fresh, clean equilibrium state
c.ramp_voltage(Vfinal=-0.5, Vstep=-0.1)

Source Code

%%capture
voltages = [0, -0.5, -1, -1.5, -2, -2.5, -3, -3.5, -4, -5, -6, -7, -8, -9, -10]
ramp_rate = -0.1

n_dist = {}
neffs = {}
clear_devsim_cache()
um = 1e-6

dev = get_simulation_xsection.PINWaveguide(
    core_width=0.500 * um,
    core_thickness=0.220 * um,
    slab_thickness=0.090 * um,
)
dev.ddsolver()     # fresh, clean equilibrium state
for ind, voltage in enumerate(voltages):
    Vinit = 0 if ind == 0 else voltages[ind - 1]
    dev.ramp_voltage(Vfinal=voltage, Vstep=ramp_rate, Vinit=Vinit)
    waveguide = dev.make_waveguide(wavelength=1.55,grid_resolution=20)
    n_dist[voltage] = waveguide.index.values
    neffs[voltage] = waveguide.n_eff[0]

Source Code

import gplugins.tidy3d as td
wg_td = td.modes.Waveguide(wavelength=1.55,
                core_width=0.5,
                core_thickness=0.22,
                slab_thickness=0.090,
                grid_resolution=50,
                core_material='si',
                clad_material='sio2',
                cache_path=None,
                overwrite=True)
wg_td.plot_field('Ex')
wg_td.n_eff[0]

np.complex128(2.5932203425309455+3.8757826065200905e-05j)

Source Code

ax = waveguide.plot_index()
ax.axes.set_ylim([0,0.5])

(0.0, 0.5)

Source Code

neffs = {0: np.complex128(2.579233149832461+4.2558454254802517e-05j),
 -0.5: np.complex128(2.579248605051533+4.20043472854569e-05j),
 -1: np.complex128(2.5792605310824923+4.1578101252069765e-05j),
 -1.5: np.complex128(2.5792684479189205+4.1298845722944675e-05j),
 -2: np.complex128(2.5792768911186554+4.100265496131908e-05j),
 -2.5: np.complex128(2.579284107736812+4.0752849952389265e-05j),
 -3: np.complex128(2.5719153080505834+4.2195904369172816e-05j),
 -3.5: np.complex128(2.5792960309736594+4.033633789155556e-05j),
 -4: np.complex128(2.57930195707953+4.012628342291738e-05j),
 -5: np.complex128(2.5793103370214245+3.9827958190374006e-05j),
 -6: np.complex128(2.5793178726112416+3.956270654250005e-05j),
 -7: np.complex128(2.579323275257858+3.935982457145146e-05j),
 -8: np.complex128(2.5719524331528962+4.084224984011639e-05j),
 -9: np.complex128(2.5793333855608185+3.901735265199731e-05j),
 -10: np.complex128(2.5793378293861204+3.888440364347489e-05j)}

neffs

{0: np.complex128(2.579233149832461+4.2558454254802517e-05j),
 -0.5: np.complex128(2.579248605051533+4.20043472854569e-05j),
 -1: np.complex128(2.5792605310824923+4.1578101252069765e-05j),
 -1.5: np.complex128(2.5792684479189205+4.1298845722944675e-05j),
 -2: np.complex128(2.5792768911186554+4.100265496131908e-05j),
 -2.5: np.complex128(2.579284107736812+4.0752849952389265e-05j),
 -3: np.complex128(2.5719153080505834+4.2195904369172816e-05j),
 -3.5: np.complex128(2.5792960309736594+4.033633789155556e-05j),
 -4: np.complex128(2.57930195707953+4.012628342291738e-05j),
 -5: np.complex128(2.5793103370214245+3.9827958190374006e-05j),
 -6: np.complex128(2.5793178726112416+3.956270654250005e-05j),
 -7: np.complex128(2.579323275257858+3.935982457145146e-05j),
 -8: np.complex128(2.5719524331528962+4.084224984011639e-05j),
 -9: np.complex128(2.5793333855608185+3.901735265199731e-05j),
 -10: np.complex128(2.5793378293861204+3.888440364347489e-05j)}

Source Code

voltage_list = sorted(neffs.items())
x, y = zip(*voltage_list)
y_array = np.array(y)
x_array = np.array(x)
dneff = y-neffs[0]
plt.plot(x, dneff)

plt.xlabel("Voltage (V)")
plt.ylabel(r"$\Delta n_{eff}$")

/home/ramprakash/anaconda3/envs/si_photo/lib/python3.13/site-packages/matplotlib/cbook.py:1719: ComplexWarning: Casting complex values to real discards the imaginary part
  return math.isfinite(val)
/home/ramprakash/anaconda3/envs/si_photo/lib/python3.13/site-packages/matplotlib/cbook.py:1355: ComplexWarning: Casting complex values to real discards the imaginary part
  return np.asarray(x, float)





Text(0, 0.5, '$\\Delta n_{eff}$')

Source Code

voltage_list = sorted(neffs.items())
x, y = zip(*voltage_list)

plt.plot(x, 10 * np.log10(k_to_alpha(np.imag(y), wavelength=1.55)))

plt.xlabel("Voltage (V)")
plt.ylabel(r"$\alpha (dB/cm)$")

Text(0, 0.5, '$\\alpha (dB/cm)$')

Source Code

c_undoped = c.make_waveguide(wavelength=1.55, perturb=False, precision="double", grid_resolution=30)
# c_undoped.compute_modes()
n_undoped = c_undoped.index.values
ax2 =  c_undoped.index.imag.plot()
ax2.axes.set_aspect("equal")
ax2.axes.set_ylim([0, 0.5])
plt.title("Imaginary part of refractive index (k)")

Text(0.5, 1.0, 'Imaginary part of refractive index (k)')

Source Code

plt.figure(figsize=(10,10))
for ind, voltage in enumerate(voltages):
    plt.subplot(5,2,ind+1)
    plt.imshow(
        np.log10(np.abs(np.imag(n_dist[voltage]- n_undoped))),
        origin="lower",
        extent=[
            -c.xmargin - c.ppp_offset - c.core_width / 2,
            c.xmargin + c.npp_offset + c.core_width / 2,
            0,
            c.clad_thickness + c.box_thickness + c.core_thickness,
        ],
    )
    plt.colorbar(label="$(|n_{doped} - n_{undoped}|)$")
    plt.xlabel("x (m)")
    plt.ylabel("y (m)")
    plt.ylim(1.72e-6, 2.5e-6)
    plt.title(f"Voltage = {voltage}V")

/tmp/ipykernel_2589823/3365713181.py:5: RuntimeWarning: divide by zero encountered in log10
  np.log10(np.abs(np.imag(n_dist[voltage]- n_undoped))),

Calacute the Vpi then have to build the compact model for the same. Finally use this in the ring resonator model

Phase change can be claculated form dn. So using this Vpi is calcaulted

Not too good - But okay for a proof of concept design

Source Code

lamda = 1.55e-6
dphi = (2*np.pi/lamda)*(dneff*1e-2)/np.pi
plt.plot(-x_array,dphi)
plt.axhline(y=1, color='r', linestyle='--')
plt.xlabel('Voltage (Reverse bias)')
plt.ylabel(r"$\Delta\phi (\pi/cm)$")

Text(0, 0.5, '$\\Delta\\phi (\\pi/cm)$')