Coupling length measurement

- May 3, 2024 at 10:40 am
  
  dubey
  Subscriber
  
  Hi, I want to study the coupling length vs radius of the ring and coupling length vs the coupling efficiency from the bus to ring waveguide (see attached figure). The structure I want to try is with simple bus bent bus and racetrack ring resonator. Can you please suggest the best way to measure the coupling length in this structure? Thank you!
- May 3, 2024 at 5:45 pm
  
  Guilin Sun
  Ansys Employee
  
  This is doable via FDTD, and possibly with FDE's help to get the proper sweep range.
  I would suggest that you first create the two waveguides (ring and the straight ) in FDE, and set proper bending radius accordingly. Then you can estimate the coupling length when you simulate the modes for the two waveguides separately, where delta_n is the difference of the neff for the two modes. You can also estimate the couling efficiency after you copy one of the modes to the global deck with overlap.
  In FDTD, you can simulate part of the ring with the straight "bent" waveguide with titled ports inside the ring, and sweep the gap/arc length.
  As for the coupling length measurement, you may define the arc length of the straight wavefuide. It is up to use for the definition.