Mach–Zehnder Interferometer (MZI)

Circuit simulation of MZI

Using SAX, GDSFactory with PDK SiEPIC

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

PDK.activate()
import sax
from jax import config
config.update("jax_enable_x64", True)
import jax.numpy as jnp
from simphony.libraries import siepic

Using MPI version 4.1, 1 processes


2025-10-28 02:20:57.788 | INFO     | gplugins.gmeep:<module>:39 - Meep '1.31.0' installed at ['/home/ramprakash/anaconda3/envs/si_photo/lib/python3.13/site-packages/meep']

Loading components from the PDK and making geometry with gdsfactory

Source Code

y_branch=cells.ebeam_y_1550()
bend = cells.bend_euler(radius=5,p=0.75)
gc = cells.ebeam_gc_te1550()

my_device = gf.Component()
y_in = my_device.add_ref(y_branch)
y_out = my_device.add_ref(y_branch)
gc_in = my_device.add_ref(gc)
gc_out = my_device.add_ref(gc)

short_waveguide=my_device.add_ref(cells.straight(10.8186))
long_waveguide=my_device.add_ref(cells.straight(20.299))
waveguide=my_device.add_ref(cells.straight(111.5))
short_waveguide2=my_device.add_ref(cells.straight(10.8186))
long_waveguide2=my_device.add_ref(cells.straight(20.299))
waveguide2=my_device.add_ref(cells.straight(122.5))

bend1 = my_device.add_ref(bend)
bend2 = my_device.add_ref(bend)
bend3 = my_device.add_ref(bend)
bend4 = my_device.add_ref(bend)

gc_in.connect('o1', y_in.ports['o1'])
short_waveguide.connect('o1', y_in.ports['o3'])
bend1.connect('o2',short_waveguide.ports['o2'])
waveguide.connect('o1',bend1.ports['o1'])
bend2.connect('o2',waveguide.ports['o2'])
short_waveguide2.connect('o2',bend2.ports['o1'])
y_out.connect('o2',short_waveguide2.ports['o1'])

long_waveguide.connect('o1', y_in.ports['o2'])
bend3.connect('o2',long_waveguide.ports['o2'])
waveguide2.connect('o1',bend3.ports['o1'])
bend4.connect('o2',waveguide2.ports['o2'])
long_waveguide2.connect('o2',bend4.ports['o1'])
y_out.connect('o3',long_waveguide2.ports['o1'])
gc_out.connect('o1', y_out.ports['o1'])

# my_device.add_port(name="o1", port=y_in.ports["o1"])
# my_device.add_port(name="o2", port=y_out.ports["o1"])

# my_device_gc=gf.components.add_grating_couplers(component=my_device)
my_device.plot()
plt.show()


# my_device_gc.name="Sample_MZI"
# my_device_gc.write_gds("Sample_MZI.gds")

Source Code

scene = my_device.to_3d()
scene.show()

Source Code

print(sax.get_ports(siepic.y_branch()))
print(sax.get_ports(siepic.waveguide()))
print(sax.get_ports(siepic.grating_coupler()))

('port_1', 'port_2', 'port_3')
('o0', 'o1')
('o0', 'o1')

Source Code

netlist={"instances": {
            "gc_in": "gc",
            "splitter": "ybranch",
            "long_wg": "waveguide",
            "short_wg": "waveguide",
            "combiner": "ybranch",
            "gc_out": "gc",
        },
        "connections": {
            "gc_in,o0": "splitter,port_1",
            "splitter,port_2": "long_wg,o0",
            "splitter,port_3": "short_wg,o0",
            "long_wg,o1": "combiner,port_2",
            "short_wg,o1": "combiner,port_3",
            "combiner,port_1": "gc_out,o0",
        },
        "ports": {
            "in": "gc_in,o1",
            "out": "gc_out,o1",
        }
        }
mzi, info = sax.circuit(
    netlist=netlist,
    models={
        "ybranch": siepic.y_branch,
        "waveguide": siepic.waveguide,
        "gc": siepic.grating_coupler,
    }
)

Source Code

sax.get_settings(mzi)

{'gc_in': {'wl': 1.55, 'pol': 'te', 'thickness': 220.0, 'dwidth': 0},
 'splitter': {'wl': 1.55, 'pol': 'te', 'thickness': 220.0, 'width': 500.0},
 'long_wg': {'wl': 1.55,
  'pol': 'te',
  'length': 0.0,
  'width': 500.0,
  'height': 220.0,
  'loss': 0.0},
 'short_wg': {'wl': 1.55,
  'pol': 'te',
  'length': 0.0,
  'width': 500.0,
  'height': 220.0,
  'loss': 0.0},
 'combiner': {'wl': 1.55, 'pol': 'te', 'thickness': 220.0, 'width': 500.0},
 'gc_out': {'wl': 1.55, 'pol': 'te', 'thickness': 220.0, 'dwidth': 0}}

Source Code

wl = jnp.linspace(1.5, 1.6, 1000)
S = mzi(wl=wl, long_wg={"length": 150.0}, short_wg={"length": 50.0})

mag = jnp.abs(S["out", "in"])**2

fig, axs = plt.subplots(2, 1, sharex=True)
axs[0].plot(wl, mag)
axs[0].set_ylabel("Transmission")
axs[1].plot(wl, 10*jnp.log10(mag))
axs[1].set_ylabel("Transmission (dB)")
axs[1].set_xlabel("Wavelength (um)")
plt.suptitle("MZI Response")
plt.show()