Learning Forum

[teddie smith]

My model is bent to one side and extends beyond the simulation area(fig1), which requires the application of periodic boundary conditions (PBC). In this state, I measured the reflectance as a function of the incident angle and noticed that certain parts of the data appeared discontinuous along certain lines (Fig 2). I am unsure whether this is due to improper simulation area settings or other factors. To perform the simulations, I used BFAST.

 

Nest, I understand that when using the farfield method, periodic BC should be recognized as PML. However, I saw some papers that used periodic BC even with the farfield. This leads me to question whether the use of periodic BC is okay when using farfield function.

To obtain incoherent light, I plan to run multiple simulations and obtain the average value of the results. Could you advise me on which parameter I should vary in order to achieve this?

Thank you

[Guilin Sun]

First things first, please make sure the simulation is periodic. You can either compare with 3by3 periods, or copy and paste the single period in a word file or other file for 3by3 periods and check if they duplicate without error. 

No, Periodic structure should use grating analysis, as the farfield projection requires the fields at the monitor edge be zero, and it is not designed for periodic structure. One may use visualizer to roughly check the farfield, but not for quantify the results.

For plane wave, you just only need to have two simulations, with orthogonal polarization, and then average the result. Please refer to this https://optics.ansys.com/hc/en-us/articles/1500006149562 

 

[teddie smith]

My simulation is periodic.

You said that BC required to be 0 when I want to calculate by farfield. If I only want to check the open shape by farfield, can I understand that there is no problem with the calculation even if the material is overlapped on BC like in my current simulation?

[Guilin Sun]

 

two things to be noted:

1: for periodic simulation, only grating analysis is accurate. even the fields at the periodic boundary happen to be zero, the farfield projection will NOT consider the periodic behavior of the device and thus it is NOT correct. The visualizer with some specified perioids is only for rough check to see diffraciton phenomenon, not for final quantified result.

2: material overlap at the boundary is ok, provided that after meshing it is still periodix discretely.