Strange transmitance of AlN straight waveguide on sapphire substrate

- July 25, 2024 at 5:38 am
  
  Minming He
  Subscriber
  
  Hello,
  I am trying to simulate a straight waveguide of AlN on sapphire substrate with air as the cladding layer. The center wavelength is 369nm. However, the transmitance shows that when the wavelength is longer than 370nm, the material does not confine the light at all. Attached is the fsp file.https://drive.google.com/file/d/1jQXW7r5ikhyjovWrGB3gikrjgSoWxzdE/view?usp=sharing
  And the transmittance of the waveguide is:
  Please take a look. Thank you and have a nice day!
- July 25, 2024 at 5:01 pm
  
  Guilin Sun
  Ansys Employee
  
  It might be already cutoff. Please try to use FDE to find where it begins to not support the confined mode. Maybe it is too thin to support mode at longger wavelength.