I want to calculate the reflection coefficient of a waveguide bragg grating like this
where w=1.2 μm, t=0.9 μm, d=250 nm, Gamma=292 nm. The length of grating region is 203 μm, i.e. 700 periods. Each period of the grating has 9 grids.
Due to the fine grid in the grating region, the simulation is quite time-consuming. So I am trying to find a appropriate simulation time. I have used 5000fs and 10000fs, however, the simulation results seem to be different:
As can be seen in the figure, there are ripples in the high reflectivity band and the maximum of reflection coefficient exceeds 1 which are abnormal.
My questions are:
How can I get the correct result?
Should I increase the simulation time and to what value the simulation time should be increased?
Attached is my project file:Grating_700period_longtime.fsp (4.2 MB)
Thanks a lot!