Can't get the similar result like that of the paper about grating coupler

dear all
recently I want to replicate the results of the GC from the paper below.

I have built the 2D FDTD model and set the relative parameter value as same as the paper’s.

But the result I get from monitor(“T”) is wrong,which as shown below.

I can’t find out the reason that cause my result wrong. Can anyone help me solve the question.Thanks a lot. Apodized Waveguide Grating Couplers for Efficient Coupling to Optical Fibers
apodized1.fsp (531.0 KB)

The user found the solution to this problem. It was caused by a different definition for the fill factor (FF) used in the simulation. The results using 1-FF agree with the reference paper.