How to calculate the modes, effective index of the fundamental TM mode, using polarization fraction

- June 17, 2021 at 2:43 am
  
  cswanson
  Subscriber
  
  I am taking the FDE Solver Course and am stuck in the "My First Simulation" Quiz and Exercise where I download the associated files to perform the exercise. I trying to understand how to get the correct answer for Exercise 1 and 2. I changed the wavelength to 1.55 um, but I don't know what to do next and how to analyze the results. I am pretty much a novice in photonics. Could I do a Webex or something so someone could walk me through this?
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- June 21, 2021 at 7:51 pm
  
  Taylor Robertson
  Ansys Employee
  
  Hello cswanson
  This question is asking for the fundamental TM mode, which you can tell by looking at the TE polarization fraction. This is a pretty standard SOI waveguide geometry where TE is fundamental and the second mode will be TM.
  So you just need to use the effective index of the second mode on the list. You can find more info on the quantities here https://support.lumerical.com/hc/en-us/articles/360034396734-FDE-solver-analysis-Mode-List-and-Deck.
  
  Although guided waves is not unique to photonics, the materials and modes are different enough from RF that it might take some getting used to. I am sure you will be more comfortable by the end of the course, as differentiating between the fundamental TE and TM modes comes up regularly. If you are still troubled I would suggest finding some references on dielectric waveguides.
  
  Best
- June 22, 2021 at 8:24 pm
  
  cswanson
  Subscriber
  
  Wow! That is amazing. I am among brilliant people at Lumerical, so I am extremely humbled by your answer. Thank you so much!!!!
- June 5, 2023 at 12:03 pm
  
  optinil
  Subscriber
  
  Hi,
  does anyone know if there a way to simulate ONLY TM modes and not TE?
  The goal here is to save some calculation time, not to postselect the modes after a 'complete' simulation.