Guilin Sun
Ansys Employee

 

Some times it can be difficult to compare experiment and simulation, in particular the material and geometry. Please refer to this post: 

Ansys Insight: Why my simulation result is different from published paper or experiment?

FDTD solves directly the Maxwell Equations. So it should give roughly the same physics, if not exactly the same due to discretization, and if the settings are correct and the device is exactly the same. So pleae carefully check your device and simulation settings.