MMI
The multimode interferometer (MMI) is one of the main components of the photonic integrated circuit.
The building steps are as follows:
Import library:
from typing import Tuple
from fnpcell import all as fp
from gpdk.components.straight.straight import Straight
from gpdk.components.taper.taper_linear import TaperLinear
from gpdk.technology import get_technology, PCell
from gpdk.technology.interfaces import CoreCladdingWaveguideType
Define class MMI:
class Mmi(PCell):
"""
Attributes:
mid_wav_core_width: defaults to 5
wav_core_width: defaults to 1
n_inputs: defaults to 1
n_outputs: defaults to 2
length: defaults to 25
transition_length: defaults to 5
trace_spacing: defaults to 2
waveguide_type: type of waveguide
Examples:
```python
TECH = get_technology()
mmi = Mmi(waveguide_type=TECH.WG.FWG.C.WIRE)
fp.plot(mmi)
```
"""
mid_wav_core_width: float = fp.PositiveFloatParam(default=5)
wav_core_width: float = fp.PositiveFloatParam(default=1)
# end_core_width=fp.PositiveFloatParam(default=0.45)
n_inputs: int = fp.PositiveIntParam(default=1)
n_outputs: int = fp.PositiveIntParam(default=2)
length: float = fp.PositiveFloatParam(default=25)
transition_length: float = fp.PositiveFloatParam(default=5)
trace_spacing: float = fp.PositiveFloatParam(default=2)
waveguide_type: CoreCladdingWaveguideType = fp.WaveguideTypeParam(type=CoreCladdingWaveguideType)
def _default_waveguide_type(self):
return get_technology().WG.FWG.C.WIRE
def build(self) -> Tuple[fp.InstanceSet, fp.ElementSet, fp.PortSet]:
insts, elems, ports = super().build()
# fmt: off
mid_wav_core_width = self.mid_wav_core_width
wav_core_width=self.wav_core_width
n_inputs = self.n_inputs
n_outputs = self.n_outputs
length = self.length
transition_length = self.transition_length
trace_spacing = self.trace_spacing
waveguide_type = self.waveguide_type
center_force_cladding_width = mid_wav_core_width+waveguide_type.cladding_width
center_type = waveguide_type.updated(core_layout_width=mid_wav_core_width, cladding_layout_width=center_force_cladding_width)
center = Straight(length=length, waveguide_type=center_type, anchor=fp.Anchor.START)
insts += center
wide_type = waveguide_type.updated(core_layout_width=wav_core_width, cladding_layout_width=waveguide_type.cladding_width + wav_core_width)
narrow_type = waveguide_type#.updated(core_layout_width=end_core_width, cladding_layout_width=waveguide_type.cladding_width + end_core_width)
taper_left = TaperLinear(length=transition_length, left_type=narrow_type, right_type=wide_type, anchor=fp.Anchor.END)
taper_right = TaperLinear(length=transition_length, left_type=wide_type, right_type=narrow_type, anchor=fp.Anchor.START)
base_in_y = - (n_inputs - 1) * trace_spacing / 2.0
for cnt in range(n_inputs):
taper_left_inst = taper_left.translated(0, base_in_y + cnt * trace_spacing)
insts += taper_left_inst
ports += taper_left_inst["op_0"].with_name(f"op_{n_inputs-cnt-1}")
base_out_y = - (n_outputs - 1) * trace_spacing / 2.0
for cnt in range(n_outputs):
taper_right_inst = taper_right.translated(length, base_out_y + cnt * trace_spacing)
insts += taper_right_inst
ports += taper_right_inst["op_1"].with_name(f"op_{cnt + n_inputs}")
# fmt: on
return insts, elems, ports
Define a MMI 1x2 class:
class Mmi1x2(Mmi, locked=True):
n_inputs: int = fp.PositiveIntParam(default=1)
n_outputs: int = fp.PositiveIntParam(default=2)
This class definition implements layout design through the following calls:
library += Mmi1x2()
fp.export_gds(library, file=gds_file)
Run and plot:
