Learning Forum

[Yuqi Meng]

I am having some trouble simulating the MZI interferometer in the Mode solution.
MY structure looks like this: While I am changing the offset of the two arms and I have put a power monitor to get the transmission rate. When I am plotting the transmission rate versus the offset. I am not getting the sinusoidal waveform but one that has ups and downs like this:
The general trend downward is clear once the phase difference goes from 0 to pi. But I cannot make sense of the oscillations. Could someone help me figure out what is the problem here?
Thank you!

[Yuqi Meng]

Different colors in the plot mean different wavelength.

[Guilin Sun]

not sure "changing the offset of the two arms " means what is changed. their distance?

Since this is a discrete simulation, which depends on the mesh, you will need to make sure the mesh does not change whehn something else is changed. You may need to use an override mesh region to fix the mesh size for the two arms, at least.

But do not set the whole simulation in uniform mesh. Otherwise the PML might not be thick enough.

[Yuqi Meng]

I am using Lumerical Mode solution, is there a way to have different densities of mesh at different regions?

[Yuqi Meng]

Thank you for the reply! The offset just means the length difference between the two arms. I will try setting the mesh size of the two arms to be the same.

[Guilin Sun]

I suggested to use override mesh:

It is local. You can round up the value, do not use too many dicimals.