Learning Forum

[Tahseen Jwad]

Hi all,
I'm new to lumerical, and I’m wondering how to get the zero-order reflection from a gratings. I’ve built this model and solve it using FDTD.

however, I’ve a feeling that the results are wrong and the reflection spectrum that I get is for the orders in this window.

ps. when I reduce the monitor size (smaller than the FDTD window size) I get different reflection behaviour 

could you please advise about how to get the zero reflection for my range of wavelength?

 

Best Regards

Tahseen

[Guilin Sun]

First, the monitor should cover the whole simulation spans in order to not miss any diffraction.

For such 1D grating, it is better to use 2D simulation, as the other dimension is infinite by use of periodic boundaries in 3D simulation.  In addition, for such 3D simulation wih 1D grating, the grating analysis can sometimes give fake diffraction orders in the uniform plane. However the diffraction strength is zero.

To get the zero-th order diffraction, please refer to this example: Diffraction grating