Autoshutoff level

skvarshneyskvarshney Member Posts: 6
edited May 8 in Photonics


I am trying to simulate a one dimensional photonic crystal cavity with FDTD boundary conditions as below:

I am getting Q factor of

Q = 90546.2 +/- 43.9683

at 190.178THz, or 1576.38 nm

  But autoshutoff level reaches till only 0.472184.

The Q factor and resonance wavelength is approximately what I want, but not sure if the simulation has run correctly or not as autoshuttoff should be around 10^-5. I have used high Q analysis group for Q factor calculation. and I have set simulation time of 50,000 fs. So, is the calculation correct??

Please suggest how to reduce the autoshuttoff level. Or can I assume my simulation is correct

If you can give any advice, it would of great help to me.


  • trobertstroberts Posts: 60Ansys Employee

    Hello Svarshney,

    Please refer to this page ,, for a discussion on how to calculate the q factor. In short the only way to reduce auto-shutoff is to allow the simulation to run longer. Using the high q analysis group; however, you should be able to get the Q factor so this is correct. This is a pretty sensitive parameter, and so an order of magnitude calculation seems pretty reasonable.

    I would consider using PML on all boundary conditions, as this will more accurately consider the Q of an isolated cavity. Currently, with Bloch you are looking at the Q factor of an infinite array of cavities. This will provide more loos channels and have the simulation run faster. You may want to move the BC further away from the cavity.


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