Optiwave Designer

I think you almost answered your own question.:) The spectral width of the CW input field is essentially zero, where as the spectral width of the Gaussian modulated CW input field can be quite large.

The half width of the spectral content is 1/T, the half width in time. For the default pulse, that corresponds to 54.8 THz half width at e^-0.5 the maximum. That means the bandwidth would be about 109 THz.

More information can be found here:

Gaussian Pulse Description [FDTD]

Cheers!

This can depend on the design and can be particularly challenging if you have a cavity, which traps the light within it. For your typical, reflection/transmission simulation you want to run the simulation long enough that the field begins to reach steady state, which generally means the electromagnetic field begins to reach 0 everywhere. You can take snapshots to see the relative magnitude of the field and wait until it becomes below 1% of the initial excitation.