# 3D DEVICE, Periodic boundary conditions

#1

For Lumerical DEVICE, is it possible to use periodic boundary conditions? This would be useful for both thermal as well as electrical simulations of periodic structures, such as interdigitated silicon photonic pn junction modulators.

Thank you
Lukas

#2

DEVICE does not have options to define periodic boundary condition like FDTD. However, the simulation boundaries in DEVICE assume symmetric boundary by default. So if your periodic structure is also symmetric then you can simply simulate a unit cell without any need of defining any special boundary conditions. For example, in this KB example (Interleaved PN Junction Microring Modulator), we have simulated a unit cell of the modulator assuming symmetry. I have shaded the simulation volume to help identify it’s extent.