Ansys Insight: Simulation plane in 2D FDTD

kghaffarikghaffari Ansys Employee Posts: 10
edited September 13 in Photonics

Is it possible to do a 2D simulation in FDTD Solutions on a plane other than the default XY plane?

By default, the FDTD solver only has 2D setting on the XY plane. That said, there are some ways to set up a quasi-2D simulation in a 3D FDTD solver, say on the XZ plane with the memory requirement on the scale of a 2D simulation.

The trick is make a 3D simulation region with a one-mesh-cell thick y span. Like this screenshot below:

To estimate the size of 1 mesh cell, you could first find the number of mesh points per wavelength (ppw) in the solver region. By default, for mesh accuracy 2, it is 10 ppw. For example at wavelength 1 um, material index =2, the size of a mesh cell in the material should be 1um/10ppw/2 = 0.05 um.

Alternatively, increase the simulation region y span and measure the size of a mesh using the Ruler.

Similarly, users can make their own quasi-2D simulation on the YZ plane using a 3D simulation, or even a quasi-1D simulation.

Note: This approach shouldn't be applied when dipole sources are used.


  • andyperkinsandyperkins Posts: 4Member

    What is the limitation preventing Lumerical to define a 2D simulation in the XZ plane instead of the XY plane? Can a rotation of axes be done?

    It would be a huge benefit not to have to do the quasi-2D simulation simply because the geometry is built in a different orientation than what Lumerical considers 2D.

  • kghaffarikghaffari Posts: 62Ansys Employee

    Hi Andy, 

    Thank you for your feedback. Aside from running a quasi-2D simulation, you can also rotate your geometries in order to perform the 2D simulation in another plane like XZ. I agree that it’d be much simpler if FDTD allowed for 2D simulation in any planes. I don’t think there’s a fundamental limitation for this; however it will require considerable updates to the algorithm. Please consider submitting this is as a feature request on our ideas exchange platform.

    All the best,


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