Generic Components

The generic template copies these components and their helper modules into your project's components/ package. Import them from components, not rosette.components, so local edits take effect:

from components import grating_coupler, mmi, ring

This page describes the starter version. Once you edit a component, its project-local source and docstring are authoritative. Use the shared component-authoring guide when modifying an included component or adding a new one.

Shared conventions

• Dimensions are in microns and geometric angles are in degrees.
• The first component parameter is the target Layer.
• Components use a canonical +X orientation and ports point outward.
• A port's width matches the physical waveguide width at that boundary.
• gap is edge-to-edge for rings and directional couplers.
• Component functions return geometry-only Cell objects. Named metric functions report unambiguous optical path lengths.

bragg_grating

bragg_grating(
    layer,
    waveguide_width=0.5,
    corrugation_width=0.05,
    period=0.32,
    num_periods=200,
    duty_cycle=0.5,
    apodization="uniform",
    apodization_sigma=0.25,
    phase_shift=None,
    phase_shift_position=0.5,
) -> Cell

Creates an inline uniform or Gaussian-apodized Bragg reflector with in and out ports. phase_shift, when provided, is in radians.

crossing

crossing(
    layer,
    waveguide_width=0.5,
    arm_length=5.0,
    crossing_type="elliptical",
    center_width=None,
) -> Cell

Creates a simple, elliptical, or MMI-style crossing centered at the origin. The west/east axis uses in1 and out1; the south/north axis uses in2 and out2.

directional_coupler

directional_coupler(
    layer,
    waveguide_width=0.5,
    coupling_length=20.0,
    gap=0.2,
    bend_length=10.0,
    port_spacing=5.0,
    num_segments=32,
) -> Cell

Creates two S-bent arms around a parallel coupling region. The gap is the edge-to-edge spacing between the coupled waveguides.

edge_coupler

edge_coupler(
    layer,
    waveguide_width=0.5,
    tip_width=0.15,
    taper_length=200.0,
    taper_profile="linear",
    cladding_layer=None,
    cladding_width=3.0,
) -> Cell

Creates an inverse taper or spot-size converter. It has one routable opt port; the narrow tip is a physical chip edge rather than a second port.

grating_coupler

grating_coupler(
    layer,
    waveguide_width=0.5,
    period=0.63,
    fill_factor=0.5,
    num_periods=25,
    grating_type="uniform",
    focusing_angle=20.0,
    grating_width=None,
    taper_length=20.0,
) -> Cell

Creates a focused coupler by default. Set focusing_angle=None for a straight grating and use grating_width to set its width. The single opt port faces +X.

mmi

mmi(
    layer,
    *,
    n_in=1,
    n_out=2,
    waveguide_width=0.5,
    length=10.0,
    mmi_width=6.0,
    taper_length=5.0,
    taper_width=1.2,
    port_separation=2.0,
) -> Cell

Creates a 1x1, 1x2, 2x1, or 2x2 MMI. A single-port side uses in or out; a two-port side uses numbered ports with 1 below 2.

ring

ring(
    layer,
    waveguide_width=0.5,
    radius=10.0,
    gap=0.2,
    coupling="allpass",
    coupling_length=0.0,
    bus_extension=5.0,
    num_segments=128,
) -> Cell

Creates a circular ring when coupling_length=0 and a racetrack otherwise. All-pass mode exposes in and out; add-drop mode exposes in, through, add, and drop.

sbend

sbend(
    layer,
    waveguide_width=0.5,
    length=20.0,
    offset=5.0,
    bend_type="cosine",
    num_segments=None,
) -> Cell

Creates a cosine, circular, or Euler-profile lateral offset. The in port is at (0, 0) and the out port is at (length, offset), with horizontal endpoint directions.

bragg_grating_length

bragg_grating_length(period, num_periods, duty_cycle, phase_shift=None) -> float

Returns the complete inline grating length, including the terminator and optional phase-shift stub.

crossing_through_length

crossing_through_length(arm_length) -> float

Returns the through length across either crossing axis.

directional_coupler_arm_length

directional_coupler_arm_length(
    bend_length,
    coupling_length,
    port_spacing,
    gap,
    waveguide_width,
    num_segments=32,
) -> float

Returns the centerline length of either symmetric coupler arm.

mmi_through_length

mmi_through_length(length, taper_length) -> float

Returns the straight through length across both tapers and the MMI body.

ring_round_trip_length

ring_round_trip_length(radius, coupling_length=0.0) -> float

Returns the ring or racetrack round-trip centerline length.

sbend_path_length

sbend_path_length(
    length,
    offset,
    bend_type="cosine",
    num_segments=None,
) -> float

Returns the numerically integrated S-bend centerline length.

Verify local changes

After editing a component, place it in a small design and run:

uv run rosette build designs/component_test.py
uv run rosette check designs/component_test.py
uv run rosette shot designs/component_test.py

The build confirms serialization, checks catch physical and connectivity problems, and the snapshot provides a visual inspection loop.