TE and TM in MZ interferometer

needattention

#1

Hi everyone:

I want to get familiar with the elements in the INTERCONNECT library, and I built a MZ interferometer. But there are some problems confused me.

In one arm of the MZ interferometer, I added a phase shifter (phase angle=0rad) and a polarization rotator (angle=pi/2) which change the TE mode into TM mode. For convenience, I wrote the OOSC results in the figure. I found that there is no TM mode at the output.

To my knowledge, the TE mode and TM mode cannot interfere so the intensity (or optical power) should be the sum of the two modes. There should be 2.5W TE mode and 2.5W TM mode at each output ports. But the simulation shows no TM mode. Please help me find my wrong settings!

I have tried to disconnect one line, as shown below, and the TM mode appears!!!

I upload the INTERCONNECT file and the SCRIPT file here.
mz.icp (424.2 KB)
mz.lsf (590 Bytes)

Thank you very much!


#2

Hello,

Please look into the example for MZ interferometer:

https://kb.lumerical.com/en/index.html?ref_primitive_elements_mach_zehnder_interferometer.html

https://kb.lumerical.com/en/index.html?ref_primitive_elements_mach_zehnder_modulator_measured.html

https://kb.lumerical.com/en/index.html?ref_primitive_elements_straight_waveguide.html

In the link below it describes how to simulate the electro-optical behavior of a Mach-Zehnder interferometer (MZI) fabricated with a silicon-on-insulator (SOI) process using the multi-physics simulation environment of DEVICE. In particular, we will calculate the spatial carrier concentration as a function of applied voltage using the CHARGE solver in DEVICE. From the carrier concentration, we can estimate the device capacitance. The carrier concentration can also be exported to the FEEM solver in DEVICE where we can calculate how the optical properties of the waveguide change as a function of applied voltage.

https://kb.lumerical.com/en/index.html?pic_modulators_getting_started_mach_zehnder.html

I would suggest that you could add a Y-branch element. The Y Branch adds up the electrical fields but not the intensity of the signals (based on the coupling coefficients), and the equation is (E1+E2)/sqrt(2)The example file.optical_y_branch.icp (263.7 KB) has some optical Oscilloscopes connected to the lasers and to the output of the Y Branch and measure the complex transmissions of the signals.

image
If you look at the complex transmission real and imaginary parts of the signals, they all follow the equation (E1+E2)/sqrt(2).
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Hope this helps!