Difference between transmission calculated using a broad-band source and using a pulse source

[asun]

Hi, I’m having trouble simulating a pulse through a photonic crystal in time domain, using FDTD Solution. At first, i used a broad-band source for transmission calculation, and then when i changed it to a ultrashort pulse (~200 fs), and detected transmission at the band edge of the structure, the result dropped by four orders of magnitude from 0.02 calculated using the broad-band source.

Why the difference in transmission between two sources is so huge? There’s no nonlinear effect and the material with any absorption set. Is it possible I set some parameters in the wrong way?

[Guilin Sun]

This is a duplicated post. The question has been answered in another post.