Error in concatenation for nested sweep



I used to be able to run the attached file before. However, now when I try to run the nested sweep it gives me concatenation error. I am using the nested sweep to change incidence angle and wavelength. I am using the newest FDTD version. I tried having an override mesh but this did not help since each simulation gives me one number only (reflection value). I read the other posts about the same error but they did not help. I am wondering if you have an idea about why I might be having this error.

Gratings - Copy.fsp (328.6 KB)


Hi @Pascal

This seems to be a bug and I have reported it. I will keep you updated once there is any progress.

Thanks for your patience.


Hi @Pascal

It seems to fix/workaround the issue if I check the “set simulation bandwidth” option in FDTD Advanced tab. Set the simulation wavelengths to 0.4 to 0.6 um. It will then “lock” the mesh and therefore make sure the size of the matrix will be all the same. The link below might be also useful for your review:
Error running nested sweep - individual results could no be concatenated



Hi @bkhanaliloo,

Many thanks for your response. I tried the method that you recommended but it did not give me the right results. I ended up having to run different simulation scenarios manually instead of having a nested sweep. In the nested sweep simulation that I upload at the beginning of this thread, each simulation gives one value for the reflection, therefore, my understanding is that varying the mesh size among different simulations should not cause issues since each simulation doesn’t produce a matrix but it produces just one number.

Thanks a lot.


Hi @Pascal

When I modified the advanced tap to set the simulation bandwidth from 650-825 as below, I did not come across the issue:

I have to look deeper to see why this solves the problem. As you mentioned, transmission is a single value and returns only an integer as a function of wavelengths.