Learning Forum

[Guilin Sun]

Hi Zhongdi, please write post in Photonics forum later.

This is mainly due to the fact that long and large device needs long simulation time. You can use much longer simulation time and let the autoshutoff min to terminate the simulation.

Mesh 0.2um might be too coarse. Suppose the wavelength in vacuum is 1.5um, refractive index 3.4, the mini wavelength inside the material is 1.5/3.4~0.44 um. so 0.2um is just above the Nyquist requirement. In order to get result with reasonable accuracy, it should be at least  0.44 um/6~0.07um, which is equivalent to mesh accuracy 1, the coarest mesh by default. Perhapes you need to upgrad your computer, as it is your tool for your projects. Please refer to the following posts:

Ansys Insight: 在FDTD 仿真的过程中mesh的精度如何设置？

Ansys Insight: 用于设置Mesh accuracy对应多大的网格尺寸

As for diverging, it depends on the mesh size. You can use thicker PML along propagation direction. To reduce memory requirement, you could use Metal BCs in y and z. Make sure the source mode is correct. 

Ansys Insight: FDTD 和 varFDTD 常见的发散原因以及处理