Today in simulation in Lumerical i faced with this error in lumerical so i want to here discuss how we can solve and continue simulation in this situation.


Warning! The simulation that created the data in the monitors and sources below diverged, and the data is likely invalid. Please see the Diverging simulation page for help on solving this problem.

So from top link we want to test and describe solving this problem.  In that link offer a trooble shooting guide to solve problem:

Determine the type of instability

Most diverging simulations fall into one of two categories. Either the simulation is diverging due to a dt stability factor problem, or a PML boundary condition problem.


It is easy to determine the type of instability by setting all of the simulation boundary conditions to Metal, then re-running the simulation.

If the simulation still diverges, it is a dt stability factor type of divergence. See the dt stability factor section.

If the simulation is stable, it is a PML type of divergence. See the PML and dispersive materials section.

For my problem when i increase frequency from 30 THz to 400 THz, i faced with this error. So to offering this top link i changed boundary condition from PML to Metal, yet i had same errors.So i switched to dt stability factor part.So i changed mesh to 8, i change dt stability factor to .1,.2,.9,.95,1 and i even change min mesh step to .1,.05,.01,all of them old error diverge.

Fig1: changing dt stability factor


After it, i used before mesh override so i started to change this parameters:

Mesh aspect ratio

A large mesh aspect ratio can cause the simulation to be unstable. If dx = 5nm and dy = 25nm, the aspect ratio is 5. In principal, there is nothing wrong with having a large aspect ratio, but in practice it can be slightly unstable when dt is near the maximum theoretical limit.

Case dx = 1nm , dy = 1nm and dz=4nm, the aspect ratio is 1 & Case dx = 4nm , dy = 4nm and dz=4nm, the aspect ratio1 we have not any success . Some other reason that may causes diverge is:

Material properties

Some dispersive material models can cause the simulation to be slightly unstable. If you discover that one of your materials causes the simulation to be unstable, use the Material explorer to ensure that the material properties are what you expect. In some cases, the automatic data fitting routine will create fits that are not very good. In this case, you should adjust the fit parameters to obtain a better fit. See this link for more details: Modify material fit. If the fit is good, then reduce the dt stability factor to make the simulation stable.


So soon i share results and failures and successes.

Other important cases that i shared here.


Lumerical software has an automatic divergence checking feature. If the total energy in the simulation volume is many times larger than the injected energy, the simulation will be stopped. The following graphical warning shown will appear in the Job Manager and Object tree when a diverging simulation is detected.







The automatic divergence checking feature properties are found in the Advanced tab of the Simulation region properties.


Time and movie monitors can be helpful when debugging diverging simulations. Both will show the fields growing exponentially at some point. Simulations that suddenly become very slow (for example, the time remaining estimate increasing from 5 minutes to 1 hour) is another sign of divergence. The automatic divergence checking normally stops the simulation before the simulation becomes very slow

So my problem is solved with changing parameters of material that i used, i used Graphene, i changed chemical potential, So my problem is solved.

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