Effective indices of first two modes in SWG

- August 17, 2023 at 4:46 pm
  
  minusunny
  Subscriber
  
  Hi,
  How can i calculate effective indices of first two modes of an subwavelength grating using FDTD ? Will using FDE work?
- August 17, 2023 at 5:08 pm
  
  Amrita Pati
  Ansys Employee
  
  Hi,
  
  You may use FDE, which is specfically developed to calculate the modes of a waveguide. Also, the mode source in FDTD has an inbuilt eignemode solver, which can also calculate the modes. But I would recommend FDE if you have the option.
  Regards,
  Amrita
- August 18, 2023 at 1:39 am
  
  minusunny
  Subscriber
  
  Will the result be accurate for SWG?
  I am trying an example given in the following link:
  How to calculate the effective index of bioperiodic SWG structures (ansys.com)
  It only gives the effective index of first mode. I would like to get effective index with second mode in similar manner. Is there any possible way to do that?
- August 18, 2023 at 5:50 pm
  
  Amrita Pati
  Ansys Employee
  
  Hello,
  Are you referring to the mode source used in a Bragg grating? By default the mode source only selects the fundamental mode.You can choose "user select", and then "select mode". This would open up the eigenmode solver and you should be able to calculate the modal properties of multiple modes.
  Regards,
  Amrita
- January 26, 2024 at 7:40 pm
  
  minusunny
  Subscriber
  
  Hello,
  I tried this. But when i try to plot. I am having different wavelength points for neff0 and neff1 while plotting may be because of using polyfit.If i remove polyfit i am not getting exact values for indices. Is there anyother way to calculate effective indices for SWGs?
  I wanted to calculate beat length for MMI.
  Lpi = wavelength/2*(neff0-neff1).
  Can i simulate SWG on EME?