long waveguide (more than 240um) gives no transmission

omniaomnia Member Posts: 3


I have a problem simulating simple and direct waveguide but the length is more than 200um. After field propagates for about 140 um, it just disappear. It is not decayed, it abruptly disappear.!!!

If I increase the x position of the source by 20um for example, the light will end at position increased by 20um from the previous step!!!! seems like the simulation cannot handle length after certain value.

I am using SiN wg (zero loss) with 'SiO2 - dispersive and lossless' clad. I am using high mesh value in y and z direction.

I tried to make the wg and clad as dielectric with fixed index to eliminate the loss, but still same result.

I also tried to increase the mode source power but also same result. The same result obtained in FDTD and varFDTD.

Does it mean I cannot simulate long devices (looks not logic)? or my simulation setup has a problem?

Thank you

Best Answer

  • gsungsun Posts: 953Ansys Employee
    edited September 9 Accepted Answer

    It is ok. I guess you know it is due to short simulation time. Usually you can set very long simulation time and use the autoshutoff min to terminate the simulation.

    Maybe you just tried to do a simple test. for straight waveguide, or uniform material, no need to simulate long distance since the fields can be calculated analytically, either using mode property, or material property and the wave.


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