Simulating an aperture with CAMFR

This simple example illustrates the integration of SlabSim in IPKISS. It requires the Luceda AWG Designer module. We make a simple aperture and run a CAMFR simulation on it.

Note: do not use this aperture in a real design, this is only for illustration purposes and not designed optimally.

Getting started

We start by importing the technology with other required modules:

from si_fab import all as pdk
import ipkiss3.all as i3
import numpy
import pylab as plt

From IPKISS’ AWG Designer and si_fab_awg, we import the following:

from awg_designer.all import SimpleSlabMode
from si_fab_awg.all import SiRibAperture, SiSlabTemplate

Template for the free propagation region. This defines the layers, slab modes, etc.

slab_t = SiSlabTemplate()
slab_t.Layout()
slab_t.SlabModes(modes=[SimpleSlabMode(name="TE0", n_eff=2.8, n_g=3.2, polarization="TE")])

<SiSlabTemplate.SlabModes view 'TEMPLATE_1:slabmodes'>

Specify the wavelength of interest in an Environment object

environment = i3.Environment(wavelength=1.55)

The aperture

Make an aperture consisting of a transition between two trace templates. Trace template at the aperture

ap_wg_t = pdk.SiRibWaveguideTemplate()
ap_wg_t.Layout(core_width=2.0)

<SiRibWaveguideTemplate.Layout view 'SI_FAB_RIB_WGTEMPLATE_2:layout'>

Trace template at the waveguide port

wg_t = pdk.SiWireWaveguideTemplate()
wg_t.Layout(core_width=0.4)

<SiWireWaveguideTemplate.Layout view 'SI_FAB_WIRE_WGTEMPLATE_2:layout'>

The aperture

ap = SiRibAperture(
    slab_template=slab_t,
    aperture_trace_template=ap_wg_t,
    trace_template=wg_t,
    taper_length=30,
)
ap_lo = ap.Layout()  # the length is calculated by default
ap_lo.visualize()
ap_lo.visualize_2d()

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<Figure size 640x480 with 1 Axes>

Get the field profile at the aperture

This will execute a CAMFR simulation. By putting verbose=True, the simulation prints the wavelength and effective indices used for the simulation.

ap_sm = ap.FieldModelFromCamfr()
f = ap_sm.get_fields(environment=environment, verbose=True)
f.visualize()

Running camfr simulation:
* Device: <LayoutCell.Layout view 'PCELL_1:layout'>
* Wavelength = 1.55 um
* Effective indices used:
  - Oxide: 1.444023622
  - 220nm Si: 2.848214685217785
  - 100nm Si: 2.1894098805166937

<Figure size 640x480 with 1 Axes>

Show the far field

ff = ap_sm.get_far_field(environment=environment)
ff.visualize()

<Figure size 640x480 with 1 Axes>

Plot the full field inside the waveguide aperture:

f2d = ap_sm.get_aperture_fields2d(environment=environment)
f2d.visualize()

<Figure size 640x480 with 1 Axes>

CircuitModel: Check the backreflection of the aperture

The circuitmodel will get this directly from the CAMFR simulation

ap_cm = ap.CircuitModel()
wavelengths = numpy.linspace(1.5, 1.6, 21)
s_matrix = ap_cm.get_smatrix(wavelengths=wavelengths)
refl_aperture = 20.0 * numpy.log10(numpy.abs(s_matrix["in", "in"]))

Plot the reflection of the aperture.

plt.plot(wavelengths, refl_aperture)
plt.xlabel("wavelength")
plt.ylabel("reflection [dB]")
plt.show()