In this demo, we are going to learn how to handle multiple modes in the primitive elements.
Let's open the ring resonator project file that we created earlier.
Now let's take another look at the properties of the waveguide element.
We can see that the waveguide contains two sets of propagation parameters for two different modes.
These modes are identified by the "orthogonal identifier".
So far, we have used the mode with orthogonal identifier 1 which is labeled as a transverse electric (TE) mode.
When propagating a particular optical mode through multiple elements, the orthogonal identifier must be identical.
To verify this, let's select the ONA and take a look at its properties.
Note that the orthogonal identifier of the source is also set to 1, which means the waveguide
will use the propagation parameters for the TE mode.
If we run the simulation with the current settings,
The transmission of the ring resonator will be calculated for the TE mode.
Let's take a look at the transmission plot.
We'll set the scalar operation to absolute value squared so that we are plotting the power transmission.
We will now run the same simulation for the TM mode.
To do this, first switch back to the design mode.
And now we'll set the orthogonal identifier for the ONA to 2
(you can also change the label to Y if you want)
Next, we will set the waveguide properties of the TM mode.
Let's select waveguide 1 and set the effective index for mode 2 to 2.3
and the group index to 3.2.
We'll select waveguide 2 and do the same
Finally, we will set the coupling coefficient for the TM mode in the waveguide couplers.
Let's set the coupling coefficient to 0.15.
We are now ready to simulate the TM mode transmission of the ring resonator.
And now are going to plot the absolute value squared of the transmission.
Note that the transmission signals already have the mode information available in the
Attribute column of the visualizer.
This information is provided by the element connected to the ONA input.
In this case it's the waveguide coupler, which has the mode labels TE and TM
for mode identifiers 1 and 2 respectively.