A Gaussian-pulse source excites the TM mode in the plasmonic slow waveguide

Dear engineer:
I would like to use the FDTD Solutions to repeat the results of this article (Plasmonic slow light waveguide and cavity). To demonstrate the slow light phenomenon, a Gaussian-pulse source located in the centre of the dielectric to excite the TM mode, with the central frequency set at 0.332wp, 0.335wp, 0.338wp, respectively. The time fluxes achieved in five different positions have been shown as follows.

but I can’t get the same result. First, the result of the monitor is not a gassian pulse,like this

How do I deal with the problem. Thank you very much.

Dear @liangshuhai

Thank you for reaching out.

I am not too familiar with the topic, and had a few questions. Do you need to use Gaussian source for exciting TM modes? Generally, if we are interested in the waveguide modes, we use Mode source and then set it to the mode of interest. More clarification will be quite useful.

Also, please share the simulation file and I will be glad to take a look at it.