Simulation time of waveguide simulations

    • kokiabe


      I'm working on simulation of topological PhC waveguide simulation.  I'm trying to observe the power and Electirc field distribution of the propagation.Source is right-cirlular polalized light, reporduced by two Dipoles. For Boundry conditons I'm using PML stabilized (Periodic for Z max), and the structure is big enough to pass through the PML. For propagation power the filed monitor is placed every 1um, and I'm observe Transmission for propagation power. FDTD region is about 10um*7um*2um. Structre itself is 200nm width membrane. Right now simlulation time is 200fs, and if I make this a little longer it will diverge. 

      What is the appropriate time to observe power and eletctric field distribution? In addition, is this the correct method to observe the power of the propagation?

      Thanks in advance.

    • Taylor Robertson
      Ansys Employee

      Hello Kokiabe,

      To analyze the PhC waveguide I would suggest following this article using bandstructure methods. This difficulty here is that there is no easy way of injecting the modes into this type of structure. The modes involved are not 2 dimensional, as they would be with a simple waveguide. So using dipoles to excite the fields and then finding the resonating frequencies should work.

      I would suggest trying to look at TE and TM modes separately. You can then consider more complicated polarizations as the superposition of these two.

      If the simulation is diverging that is an issue. Perhaps try changing all materials to "object defined dielectric" and PEC, for dielectrics and metals respectively. If this converges check your material fits, and make sure there is no artifical gain in the fitting. This is an example of material divergence. If not try setting BC to metal. If that converges it is PML instabillity. In that case maybe move them further away, or share a screenshot of the set-up.

      To get the field profile determine the frequencies. Then set your frequency monitors to this exact frequency. It is best to apodize the signal to eliminate contributions from the initial injection. You can likely determine the loss from the decay of the time signal, assuming it is not too lossy.


      Best Regards,



    • kokiabe

      Thank you for the reply, and I apologize for not responsing earlyer.

      >>You can likely determine the loss from the decay of the time signal, assuming it is not too lossy.

      Do you mean using time monitor, when obtaining time signal?



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