Sample circuit layout with ltoi300 PDK

Here we provide an example of PIC layout with the ltoi300 PDK. We start by choosing a die floorplan compatible with a submission for an LXT MPW run, then place some edge couplers for I/O at the right locations on the chip frame. We create a circuit cell with an evanescently-coupled ring resonator and connect it with the input and output edge couplers. We also create travelling wave modulators and route them optically to I/O edge couplers and electrically to wirebond pads.

from functools import partial
from pathlib import Path

import gdsfactory as gf
import numpy as np
from gdsfactory.routing import route_bundle

import ltoi300  # noqa: F401  – activates the PDK
from ltoi300.tech import LAYER

Choose the chip format and display the outline

@gf.cell
def chip_frame():
    c = gf.get_component("chip_frame", size=(10_000, 5000), center=(0, 0))
    return c

chip_layout = chip_frame()
chip_layout

Get the O-band ring resonator and edge couplers

ring_resonator_oband = gf.get_component("ring_resonator_single_mode_point_coupler_oband")
ring_resonator_oband

Note that we place the edge couplers such that the input port is slightly sticking outside of the chip footprint on the CHIP_EXCLUSION_ZONE layer. This is the correct placement for die singulation.

x_in = chip_layout.dxmin + 100.0
in_loc = np.array([x_in, chip_layout.dymax])
out_loc = np.array(
    [x_in + 2.5 * ring_resonator_oband.settings["ring_radius"], chip_layout.dymin]
)

ec_in = gf.Component()
ec_oband = gf.get_component("edge_coupler_oband")
ec_ref = ec_in << ec_oband
ec_ref.drotate(-90.0)
ec_ref.dmove(
    ec_ref.ports["o1"].dcenter, in_loc + [0.0, 0.5 * ec_oband.settings["input_ext"]]
)
ec_in.add_ports(ec_ref.ports)

ec_out = gf.Component()
ec_ref = ec_out << ec_oband
ec_ref.drotate(90.0)
ec_ref.dmove(
    ec_ref.ports["o1"].dcenter, out_loc - [0.0, 0.5 * ec_oband.settings["input_ext"]]
)
ec_out.add_ports(ec_ref.ports)

ecs_oband = {
    "in": ec_in,
    "out": ec_out,
}

Get the C-band ring resonator and edge couplers

ring_resonator_cband = gf.get_component("ring_resonator_single_mode_point_coupler_cband")
ring_resonator_cband

x_in = chip_layout.dxmin + 200.0  # 100 um pitch from O-band ring EC (dxmin + 100)
in_loc = np.array([x_in, chip_layout.dymax])
out_loc = np.array(
    [x_in + 2.5 * ring_resonator_oband.settings["ring_radius"], chip_layout.dymin]
)

ec_in = gf.Component()
ec_cband = gf.get_component("edge_coupler_cband")
ec_ref = ec_in << ec_cband
ec_ref.drotate(-90.0)
ec_ref.dmove(
    ec_ref.ports["o1"].dcenter, in_loc + [0.0, 0.5 * ec_cband.settings["input_ext"]]
)
ec_in.add_ports(ec_ref.ports)

ec_out = gf.Component()
ec_ref = ec_out << ec_cband
ec_ref.drotate(90.0)
ec_ref.dmove(
    ec_ref.ports["o1"].dcenter, out_loc - [0.0, 0.5 * ec_cband.settings["input_ext"]]
)
ec_out.add_ports(ec_ref.ports)

ecs_cband = {
    "in": ec_in,
    "out": ec_out,
}

routing_roc = 60.0


@gf.cell
def ring_pass_circuit(
    communication_band="oband",
) -> gf.Component:
    if communication_band == "oband":
        ecs = ecs_oband
        coupled_ring = ring_resonator_oband
    elif communication_band == "cband":
        ecs = ecs_cband
        coupled_ring = ring_resonator_cband
    else:
        raise ValueError("communication_band must be either 'oband' or 'cband'")

    c = gf.Component()
    ring_ref = c << coupled_ring
    ring_ref.dmovex(
        -ring_ref.ports["o1"].dcenter[0] + ecs["out"].ports["o1"].dcenter[0]
    )
    if communication_band == "cband":
        ring_ref.dmovey(550.0)  # shift C-band ring 550 um higher

    # Bend spec

    routing_bend = partial(
        gf.components.bend_euler,
        radius=routing_roc,
        with_arc_floorplan=True,
    )

    # Routing to I/O

    [c << ec for ec in ecs.values()]

    route_bundle(
        c,
        ports1=[ring_ref.ports["o2"]],
        ports2=[ecs["in"].ports["o2"]],
        start_straight_length=5.0,
        end_straight_length=5.0,
        cross_section="xs_rwg700" if communication_band == "oband" else "xs_rwg900",
        bend=routing_bend,
        radius=routing_roc,
        straight="straight_rwg700_oband"
        if communication_band == "oband"
        else "straight_rwg900_cband",
    )
    route_bundle(
        c,
        ports1=[ring_ref.ports["o1"]],
        ports2=[ecs["out"].ports["o2"]],
        start_straight_length=5.0,
        end_straight_length=5.0,
        cross_section="xs_rwg700" if communication_band == "oband" else "xs_rwg900",
        bend=routing_bend,
        radius=routing_roc,
        straight="straight_rwg700_oband"
        if communication_band == "oband"
        else "straight_rwg900_cband",
    )
    text_ref = c << gf.components.text(
        f"{communication_band}" + "_ring", layer=LAYER.LABELS, size=13
    )
    text_ref.dmove(
        (
            ring_ref.dxmin + coupled_ring.settings["ring_radius"],
            (ring_ref.dymin + ring_ref.dymax) / 2,
        )
    )

    c.flatten()
    c.add_port(name="o1", port=ecs["in"].ports["o1"])
    c.add_port(name="o2", port=ecs["out"].ports["o1"])

    return c

Assemble the O-band circuit

circuit_oband = ring_pass_circuit(communication_band="oband")
circuit_oband

Assemble the C-band circuit

circuit_cband = ring_pass_circuit(communication_band="cband")
circuit_cband

Get the O-band terminated EO modulator and edge couplers

modulator_oband = gf.get_component(
    "terminated_mzm_1x2mmi_oband", modulation_length=6800.0, length_imbalance=120.0
)
modulator_oband

x_in = chip_layout.dxmin + 800.0
x_out = chip_layout.dxmax - 100.0
in_loc = np.array([x_in, chip_layout.dymax])
out_loc = np.array([x_out, chip_layout.dymin])

ec_in = gf.Component()
ec_oband = gf.get_component("edge_coupler_oband")
ec_ref = ec_in << ec_oband
ec_ref.drotate(-90.0)
ec_ref.dmove(
    ec_ref.ports["o1"].dcenter, in_loc + [0.0, 0.5 * ec_oband.settings["input_ext"]]
)
ec_in.add_ports(ec_ref.ports)

ec_out = gf.Component()
ec_ref = ec_out << ec_oband
ec_ref.drotate(90.0)
ec_ref.dmove(
    ec_ref.ports["o1"].dcenter, out_loc - [0.0, 0.5 * ec_oband.settings["input_ext"]]
)
ec_out.add_ports(ec_ref.ports)

ecs_oband_modulator = {
    "in": ec_in,
    "out": ec_out,
}

Wirebonding pads

We add some metal pads close to the top edge of the chip. We then guide some electrical routing traces in the top metal layer to connect with the thermo-optical shifters of the modulators. This will facilitate electrical packaging and driving the heaters from an external circuit board.

@gf.cell
def bondpad_array(
    pad_size: tuple = (170, 170),
    pitch: float = 300,
    N: int = 4,
    chip_frame: gf.Component = chip_layout,
    dx: float = 1400.0,
    dy: float = 4800.0,
):
    c = gf.Component()

    pad = gf.components.pad(
        size=pad_size,
        layer=LAYER.M2,
    )
    bp = c << gf.components.pad_array(
        pad=pad,
        columns=N,
        column_pitch=pitch,
        layer=LAYER.M2,
        auto_rename_ports=True,
        centered_ports=True,
        port_orientation=-90.0,
    )

    bp.dmove(
        origin=(bp.dxmin, bp.dymin),
        destination=(chip_frame.dxmin + dx, chip_frame.dymin + dy),
    )


    c.add_ports(bp.ports)

    return c


bp_array = bondpad_array()
bp_array

Get the C-band terminated EO modulator and edge couplers

modulator_cband = gf.get_component(
    "terminated_mzm_1x2mmi_cband", modulation_length=6800.0, length_imbalance=120.0
)
modulator_cband

/opt/hostedtoolcache/Python/3.12.12/x64/lib/python3.12/site-packages/kfactory/decorators.py:406: UserWarning: via_array: 'signal' conductor cannot fit via rows (num_rows=0); using single solid opening.
  cell = f(**params)  # type: ignore[call-arg]

x_in = chip_layout.dxmin + 750.0
x_out = chip_layout.dxmax - 200.0
in_loc = np.array([x_in, chip_layout.dymax])
out_loc = np.array([x_out, chip_layout.dymin])

ec_in = gf.Component()
ec_cband = gf.get_component("edge_coupler_cband")
ec_ref = ec_in << ec_cband
ec_ref.drotate(-90.0)
ec_ref.dmove(
    ec_ref.ports["o1"].dcenter, in_loc + [0.0, 0.5 * ec_cband.settings["input_ext"]]
)
ec_in.add_ports(ec_ref.ports)

ec_out = gf.Component()
ec_ref = ec_out << ec_cband
ec_ref.drotate(90.0)
ec_ref.dmove(
    ec_ref.ports["o1"].dcenter, out_loc - [0.0, 0.5 * ec_cband.settings["input_ext"]]
)
ec_out.add_ports(ec_ref.ports)

ecs_cband_modulator = {
    "in": ec_in,
    "out": ec_out,
}

Assembly of the modulator

routing_roc = 60.0

@gf.cell
def modulator_circuit(
    communication_band="oband",
    modulator_x_pos=-4000.0,
    modulator_y_pos=2000.0,
    bp_port_names: tuple = ("e3", "e4"),  # hashable port name strings
    waypoints_heater_routing: list = None,
) -> gf.Component:
    if communication_band == "oband":
        ecs = ecs_oband_modulator
        modulator = modulator_oband
    elif communication_band == "cband":
        ecs = ecs_cband_modulator
        modulator = modulator_cband
    else:
        raise ValueError("communication_band must be either 'oband' or 'cband'")

    c = gf.Component()
    mod_ref = c << modulator
    mod_ref.dmove(mod_ref.ports["o1"].dcenter, [modulator_x_pos, modulator_y_pos])
    # Bend spec

    routing_bend = partial(
        gf.components.bend_euler,
        radius=routing_roc,
        with_arc_floorplan=True,
    )

    # Routing to I/O

    [c << ec for ec in ecs.values()]

    route_bundle(
        c,
        ports1=[mod_ref.ports["o1"]],
        ports2=[ecs["in"].ports["o2"]],
        start_straight_length=5.0,
        end_straight_length=5.0,
        cross_section="xs_rwg700" if communication_band == "oband" else "xs_rwg900",
        bend=routing_bend,
        radius=routing_roc,
        straight="straight_rwg700_oband"
        if communication_band == "oband"
        else "straight_rwg900_cband",
    )

    route_bundle(
        c,
        ports1=[mod_ref.ports["o2"]],
        ports2=[ecs["out"].ports["o2"]],
        start_straight_length=5.0,
        end_straight_length=5.0,
        cross_section="xs_rwg700" if communication_band == "oband" else "xs_rwg900",
        bend=routing_bend,
        radius=routing_roc,
        straight="straight_rwg700_oband"
        if communication_band == "oband"
        else "straight_rwg900_cband",
    )

    # Routing to bondpad
    heater_routing_width = 40.0
    route_bundle(
        c,
        ports1=[mod_ref.ports["e3"], mod_ref.ports["e4"]],
        ports2=[bp_array.ports[bp_port_names[0]], bp_array.ports[bp_port_names[1]]],
        bend=gf.components.bend_circular,
        straight=gf.components.straight,
        auto_taper=False,
        allow_width_mismatch=True,
        layer=LAYER.M2,
        route_width=heater_routing_width,
        waypoints=waypoints_heater_routing,
        separation=10.0,
    )



    text_ref = c << gf.components.text(
        f"{communication_band}" + "_modulator", layer=LAYER.LABELS, size=13
    )
    text_ref.dmove(
        ((mod_ref.dxmin + mod_ref.dxmax) / 2, (mod_ref.dymin + mod_ref.dymax) / 2 + 100)
    )

    c.flatten()
    c.add_port(name="o1", port=ecs["in"].ports["o1"])
    c.add_port(name="o2", port=ecs["out"].ports["o1"])
    c.add_port(name="ht1", port=bp_array.ports[bp_port_names[0]])
    c.add_port(name="ht2", port=bp_array.ports[bp_port_names[1]])

    return c

modulator_circuit_oband = modulator_circuit(
    "oband", modulator_x_pos=-4000.0, modulator_y_pos=1650.0, bp_port_names=("e2", "e1")
)
modulator_circuit_oband

modulator_circuit_cband = modulator_circuit(
    "cband", modulator_x_pos=-4100.0, modulator_y_pos=650.0, bp_port_names=("e4", "e3"), waypoints_heater_routing=[(-4100, 1400), (-4100, 2200), (-3600, 2200)]
)
modulator_circuit_cband

Assemble on the die outline

@gf.cell
def die_assembled(
    chip_layout=chip_layout,
) -> gf.Component:
    c = gf.Component()
    c << chip_layout
    c << circuit_oband
    c << circuit_cband
    c << modulator_circuit_oband
    c << modulator_circuit_cband
    c << bp_array

    c.add_ports(circuit_oband.ports, prefix="oband_ring_")
    c.add_ports(circuit_cband.ports, prefix="cband_ring_")
    c.add_ports(modulator_circuit_oband.ports, prefix="oband_modulator_")
    c.add_ports(modulator_circuit_cband.ports, prefix="cband_modulator_")

    return c


die = die_assembled()
die.plot()
die.show()
_ = die.write_gds(gdsdir=Path.cwd())

Recap the port positions for testing

die.pprint_ports()

┏━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━┳━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━┓
┃ name                ┃ width ┃ orientation ┃ layer          ┃ center             ┃ port_type  ┃
┡━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━╇━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━┩
│ oband_ring_o1       │ 0.35  │ 90.0        │ LT_SLAB (3/10) │ (-4950.0, 2530.0)  │ optical    │
│ oband_ring_o2       │ 0.35  │ 270.0       │ LT_SLAB (3/10) │ (-4450.0, -2530.0) │ optical    │
│ cband_ring_o1       │ 0.5   │ 90.0        │ LT_SLAB (3/10) │ (-4850.0, 2530.0)  │ optical    │
│ cband_ring_o2       │ 0.5   │ 270.0       │ LT_SLAB (3/10) │ (-4350.0, -2530.0) │ optical    │
│ oband_modulator_o1  │ 0.35  │ 90.0        │ LT_SLAB (3/10) │ (-4250.0, 2530.0)  │ optical    │
│ oband_modulator_o2  │ 0.35  │ 270.0       │ LT_SLAB (3/10) │ (4950.0, -2530.0)  │ optical    │
│ oband_modulator_ht1 │ 170.0 │ 270.0       │ M2 (22/0)      │ (-2965.0, 2360.0)  │ electrical │
│ oband_modulator_ht2 │ 170.0 │ 270.0       │ M2 (22/0)      │ (-2665.0, 2360.0)  │ electrical │
│ cband_modulator_o1  │ 0.5   │ 90.0        │ LT_SLAB (3/10) │ (-4300.0, 2530.0)  │ optical    │
│ cband_modulator_o2  │ 0.5   │ 270.0       │ LT_SLAB (3/10) │ (4850.0, -2530.0)  │ optical    │
│ cband_modulator_ht1 │ 170.0 │ 270.0       │ M2 (22/0)      │ (-3565.0, 2360.0)  │ electrical │
│ cband_modulator_ht2 │ 170.0 │ 270.0       │ M2 (22/0)      │ (-3265.0, 2360.0)  │ electrical │
└─────────────────────┴───────┴─────────────┴────────────────┴────────────────────┴────────────┘

Clear the gdsfactory cache

gf.clear_cache()