Hi Scott,
Thanks for the response.
1. I have done the 2D simulation for the designed structure.
2. I have also placed the input source outside the structure.
3. As per your suggestion, I have broaden the input waveguide by removing a row of rods. But again a lot of power is leaking out from the waveguide as shown in the attached file.
4. I have also simulated the structure at different mesh sizes like 0.04, 0.038, 0.01 etc. but getting almost same results each time.
I am getting very confused. Please guide me on what am I doing wrong?