# Step 2: Building circuits¶

Result

We assemble a circuit using existing components, visualize the layout and perform a circuit simulation of the entire circuit.

Circuit of a ring resonator coupled to a grating coupler.

Illustrates

1. how to build a circuit using place and route.
2. how to perform a circuit simulation of a circuit.

How to run this example

To run the example, run execute_02_circuit.py.

## Making the building blocks¶

The first step is to instantiate the building blocks we will use. As shown in step-1 of this tutorial we instantiate a ring drop filter and a grating coupler.

# 1.  Importing the technology file.
from technologies import silicon_photonics
from ipkiss3 import all as i3

# 2. Import other python libraries.
import numpy as np
import pylab as plt

# 3. Creating the ring resonator
from picazzo3.filters.ring import RingRect180DropFilter
my_ring = RingRect180DropFilter()

cp = dict(cross_coupling1=1j*0.3**0.5,
straight_coupling1=0.7**0.5) #The coupling from bus to ring and back

my_ring_cm = my_ring.CircuitModel(ring_length=2 * np.pi * my_ring_layout.bend_radius, # we can manually specify the ring length, or take it from the layout
coupler_parameters=[cp, cp]) # 2 couplers

# 4. Creating the grating coupler.
from picazzo3.fibcoup.curved import FiberCouplerCurvedGrating
my_grating = FiberCouplerCurvedGrating()
my_grating_layout = my_grating.Layout(n_o_lines=24, period_x=0.65, box_width=15.5)
my_grating_cm = my_grating.CircuitModel(center_wavelength=1.55,
bandwidth_3dB=0.06,
peak_transmission=0.60**0.5,
reflection=0.05**0.5)



## Layout¶

The simplest way of building circuits in IPKISS is to use :py:classi3.Circuit<ipkiss3.all.Circuit>. This allows you to specify from which cell or subcircuit instances your circuit is composed and how they should be placed and connected.

• The layout will be automatically generated using i3.place_and_route internally.
• The netlist and model are automatically derived.

You need to specify:

• insts : a dictionary that maps the name of an instance to its corresponding cell. There can be multiple instances of each cell.
• specs : a list of placement specifications and connector specifications between ports. The supported placement specifications and connectors can be found under the i3 namespace (see also Placement and routing reference and Connector reference). We identify the terms through the name of the instance and the name of the term, like inst:term. The terms of the PICAZZO ring resonators are named in1, in2, out1, out2. The terms of the grating couplers are called out and vertical_in.
distance_x = 100.0
distance_y = 30.0

my_circuit = i3.Circuit(
insts={
'in_grating': my_grating,
'pass_grating': my_grating,
'drop_grating': my_grating,
'ring': my_ring
},
specs=[
i3.Place('ring', (0, 0)),
i3.Place('in_grating', (-distance_x, -distance_y)),
i3.Place('pass_grating', (distance_x, -distance_y), angle=180),
i3.Place('drop_grating', (-distance_x, distance_y)),
i3.ConnectManhattan([
("in_grating:out", "ring:in1"),
("pass_grating:out", "ring:out1"),
("drop_grating:out", "ring:out2"),
])
],
exposed_ports={
'drop_grating:vertical_in': 'drop',
'in_grating:vertical_in': 'in',
'pass_grating:vertical_in': 'pass'
}
)

my_circuit_layout = my_circuit.Layout()



Layout of a ring resonator connected to grating couplers.

## CircuitModel¶

The circuit model of an i3.Circuit is automatically composed from the circuit models of all of its subcomponents. The default simulation model of the waveguide extracts its length from the layout. This is a very powerful technique in IPKISS; this means you can run post-layout simulations to get an accurate representation of the circuit behavior, taking into account layout-dependent properties of the system.

my_circuit_cm = my_circuit.CircuitModel()
wavelengths = np.linspace(1.50, 1.6, 2001)
S = my_circuit_cm.get_smatrix(wavelengths=wavelengths)

# 7. Plot
plt.figure()
plt.plot(wavelengths, np.abs(S['in', 'pass'])**2, 'b', label="pass")
plt.plot(wavelengths, np.abs(S['in', 'drop'])**2, 'r', label="drop")
plt.plot(wavelengths, np.abs(S['in', 'in'])**2, 'k', label="reflection")
plt.legend()
plt.show()


In the simulation, you clearly see the interference fringes that are obtained due to the reflections in grating couplers. The period of those fringes is based on the distance between the grating couplers and that information is obtained form the LayoutView. If you modify your layout - the simulations will follow accordingly.

Note

The terms of our circuit component (these are all the terms that are not connected) are exposed and renamed by i3.expose_ports) in _generate_ports.

Transmission and reflection spectra of a ring resonator connected to grating couplers, obtained by circuit simulation.

You have just finished your first tutorial!

### Recap¶

In this tutorial you learned how to assemble a circuit based on existing Picazzo components. You can also learn how to write your own (hierarchical) components from scratch. This is the subject of the next tutorials.

Take me back to the overview!