bend_circular

Circular bending is the most common bend using in a photonic integrated circuit. This section teaches you how to create a circular bend.

Steps are as follows:

Import Library:

from functools import cached_property
from typing import Optional, Tuple

from fnpcell import all as fp
from gpdk.technology import get_technology, PCell
from gpdk.technology.interfaces import CoreCladdingWaveguideType

Define BendCircular class:

class BendCircular(fp.IWaveguideLike, fp.PCell):

    degrees: float = fp.DegreeParam(default=90, min=-180, max=180, doc="Bend angle in degrees")
    radius: float = fp.PositiveFloatParam(default=10, doc="Bend radius")
    waveguide_type: fp.IWaveguideType = fp.WaveguideTypeParam(doc="Waveguide parameters")
    port_names: fp.IPortOptions = fp.PortOptionsParam(count=2, default=["op_0", "op_1"])

    def _default_waveguide_type(self):
        return get_technology().WG.FWG.C.WIRE

    def __post_pcell_init__(self):
        assert fp.is_nonzero(self.degrees)

    @cached_property
    def raw_curve(self):
        return fp.g.EllipticalArc(
            radius=self.radius,
            final_degrees=self.degrees,
        )

    def build(self) -> Tuple[fp.InstanceSet, fp.ElementSet, fp.PortSet]:
        insts, elems, ports = super().build()
        wg = self.waveguide_type(curve=self.raw_curve).with_ports(self.port_names)
        insts += wg
        ports += wg.ports
        return insts, elems, ports

Define BendCircular at 90 degree angle:

class BendCircular90(BendCircular):
    degrees: float = fp.DegreeParam(default=90, locked=True)
    waveguide_type: fp.IWaveguideType = fp.WaveguideTypeParam(locked=True)

This class definition implements layout design through the following calls:

library += BendEuler()
library += BendEuler90()
fp.export_gds(library, file=gds_file)

Run and plot: