Amrita Pati
Ansys Employee

Hi Rony,

As you can see on the left side, the simulation has diverged so your results are not accurate. BFAST simulations are numerically more unstable than FDTD simulations. The following link provides more information on the possible causes of divergence and the steps to address it. Please go through the article and let me know if you have any questions.

https://optics.ansys.com/hc/en-us/articles/360034902273-Broadband-Fixed-Angle-Source-Technique-BFAST-

Regards,
Amrita