Transmittance at through port of grating assisted ring resonator



Hello Sir,
I want to study transmittance of ring resonator having grating structure in coupling region. xy
Transmittance at through port, T>1 with wavelength which is a strange response. While response at drop port is as it should be

The problem usually does not arise if grating is absent in coupling region.
In my simulation, early shutoff (min) was unchecked, dt stability factor = 0.4, broadband fundamental mode having 50 nm span was used. Log file of the simulation is here:grating coupled ORR.log (10.3 KB)
It will be very helpful for me if any comment to troubleshoot this problem I can find.