from __future__ import annotations
import gdsfactory as gf
from gdsfactory.component import Component
from gdsfactory.components.taper import taper as taper_function
from gdsfactory.typings import ComponentFactory, CrossSectionSpec
[docs]
@gf.cell
def mmi_90degree_hybrid(
width: float = 0.5,
width_taper: float = 1.7,
length_taper: float = 40.0,
length_mmi: float = 175.0,
width_mmi: float = 10.0,
gap_mmi: float = 0.8,
straight: ComponentFactory = "straight",
cross_section: CrossSectionSpec = "strip",
) -> Component:
r"""90 degree hybrid based on a 4x4 MMI.
Default values from Watanabe et al.,
"Coherent few mode demultiplexer realized as a
2D grating coupler array in silicon", Optics Express 28(24), 2020
It could be interesting to consider the design in Guan et al.,
"Compact and low loss 90° optical hybrid on a silicon-on-insulator
platform", Optics Express 25(23), 2017
Args:
width: input and output straight width.
width_taper: interface between input straights and mmi region.
length_taper: into the mmi region.
length_mmi: in x direction.
width_mmi: in y direction.
gap_mmi: (width_taper + gap between tapered wg)/2.
straight: straight function.
with_bbox: box in bbox_layers and bbox_offsets avoid DRC sharp edges.
cross_section: spec.
.. code::
length_mmi
<------>
________
| |
__/ \__
signal_in __ __ I_out1
\ /_ _ _ _
| | _ _ _ _| gap_mmi
| \__
| __ Q_out1
| /
| |
|
__/ \__
LO_in __ __ Q_out2
\ /_ _ _ _
| | _ _ _ _| gap_mmi
| \__
| __ I_out2
| /
| ________|
<->
length_taper
"""
c = gf.Component()
gap_mmi = gf.snap.snap_to_grid(gap_mmi, grid_factor=2)
w_mmi = width_mmi
w_taper = width_taper
taper = taper_function(
length=length_taper,
width1=width,
width2=w_taper,
cross_section=cross_section,
)
x = gf.get_cross_section(cross_section)
_ = c << gf.get_component(
straight,
length=length_mmi,
width=w_mmi,
cross_section=cross_section,
)
y_signal_in = gap_mmi * 3 / 2 + width_taper * 3 / 2
y_lo_in = -gap_mmi / 2 - width_taper / 2
ports = [
# Inputs
gf.Port(
"signal_in",
orientation=180,
center=(0, y_signal_in),
width=w_taper,
cross_section=x,
),
gf.Port(
"LO_in",
orientation=180,
center=(0, y_lo_in),
width=w_taper,
cross_section=x,
),
# Outputs
gf.Port(
"I_out1",
orientation=0,
center=(length_mmi, y_signal_in),
width=w_taper,
cross_section=x,
),
gf.Port(
"Q_out1",
orientation=0,
center=(length_mmi, y_signal_in - gap_mmi - w_taper),
width=w_taper,
cross_section=x,
),
gf.Port(
"Q_out2",
orientation=0,
center=(length_mmi, y_lo_in),
width=w_taper,
cross_section=x,
),
gf.Port(
"I_out2",
orientation=0,
center=(length_mmi, y_lo_in - gap_mmi - w_taper),
width=w_taper,
cross_section=x,
),
]
for port in ports:
taper_ref = c << taper
taper_ref.connect(port="o2", other=port)
c.add_port(name=port.name, port=taper_ref.ports["o1"])
c.flatten()
x.add_bbox(c)
return c
if __name__ == "__main__":
c = mmi_90degree_hybrid()
c.show()
