Circuit layout

Here we provide an example of PIC layout with the lnoi400 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. Finally we create a circuit cell with an evanescently-coupled ring resonator and connect it with the input and output edge couplers.

from functools import partial
from pathlib import Path
import numpy as np
import lnoi400
import gdsfactory as gf

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 circuit building blocks

input_ext = 10.0
double_taper = gf.get_component("double_linear_inverse_taper",
                                input_ext=input_ext,
                                )

coupler_gap = 0.6
ring_radius = 100.0
ring_width = 2.0
wg_width = 1.0

ring = gf.components.ring(
    layer="LN_RIDGE",
    radius=ring_radius,
    width=ring_width,
    angle_resolution=0.15,
)

dc_wg = gf.components.straight(
    length = ring_radius * 2,
    cross_section="xs_rwg1000",
)

@gf.cell
def ring_with_coupler(
    ring=ring,
    bus=dc_wg,
    gap=coupler_gap,
) -> gf.Component:

    c = gf.Component()
    ring_ref = c << ring
    coupler_ref = c << bus
    coupler_ref.drotate(90)
    coupler_ref.dcenter = [
        ring_ref.dxmax + gap + 0.5 * wg_width, 0.0
        ]
    c.add_ports(coupler_ref.ports)
    c.flatten()
    return c

coupled_ring = ring_with_coupler()
coupled_ring

Circuit assembly

Positioning of the I/O couplers

x_in = chip_layout.dxmin + 1000.0
in_loc = np.array([x_in, chip_layout.dymax])
out_loc = np.array([x_in + 2.5 * ring_radius, chip_layout.dymin])

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

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

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

Connecting the ring with I/O

routing_roc = 75.0

@gf.cell
def ring_pass_circuit(
    coupled_ring = coupled_ring,
    ecs = ecs,
) -> gf.Component:

    c = gf.Component()
    ring_ref = c << coupled_ring
    ring_ref.dmovex(- ring_ref.ports["o1"].dcenter[0] + ecs["out"].ports["o1"].dcenter[0])

    # 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()]

    gf.routing.route_single(
        c,
        ring_ref.ports["o2"],
        ecs["in"].ports["o2"],
        start_straight_length=5.0,
        end_straight_length=5.0,
        cross_section="xs_rwg1000",
        bend=routing_bend,
    )

    gf.routing.route_single(
        c,
        ring_ref.ports["o1"],
        ecs["out"].ports["o2"],
        start_straight_length=5.0,
        end_straight_length=5.0,
        cross_section="xs_rwg1000",
        bend=routing_bend,
    )

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

    return c

circuit = ring_pass_circuit()
circuit

Assemble on the die outline

@gf.cell
def die_assembled(
    chip_layout = chip_layout,
    circuit = circuit,
) -> gf.Component:
    c = gf.Component()
    c << chip_layout
    c << circuit
    c.add_ports(circuit.ports)
    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 ┃
┡━━━━━━╇━━━━━━━╇━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━┩
│ o1   │ 0.25  │ 90.0        │ LN_SLAB (3/0) │ (-4050.0, 2530.0)  │ optical   │
│ o2   │ 0.25  │ 270.0       │ LN_SLAB (3/0) │ (-3800.0, -2530.0) │ optical   │
└──────┴───────┴─────────────┴───────────────┴────────────────────┴───────────┘

Clear the gdsfactory cache

gf.clear_cache()