Guilin Sun
Ansys Employee

FDTD is a discretized method. Therefore the meshing can affect the result. You know the locations of the VCSEL layers. If they can hold integer number of meshes, it is better to use override mesh to have conformal mesh to the layer interfaces. For the DBR reflectors you can also use the two alternative layers to have integer number of meshes if each layer cannot hold, if possible.  If not, the conformal variant 0 can be used by default, to resolve sub-mesh size. With higher mesh accuracy or smaller mesh size the resonant wavelength can shift a little, but it should be very close to experiment.