Fail to find a bandgap for 1-d PC cavity


I am a really new beginner for FDTD. I am trying to simulate 1D PC cavity follow this paper( When I try to simulate figure 2 (b), I encounter some problems I get a band diagram which has no band gap. I guess maybe I misunderstand something. This is my simulation. helper.fsp (4.0 MB)
and some results derived from my simulation.

Power coupling from one fiber to another

Dear @iambud

Thank you for reaching out. Linked paper is one of my favourite papers for designing 1D PC cavities and I will be happy to be of a help.

Since you are new to the software, you can start with some of KB application examples linked below:

To calculate the bandgap, you will need only one unit cell. Since your cavity is 1D, the y and z boundary conditions need to be PML. Also, you need to define the width (thickness) of PC cavity and increase FDTD y-span (z-span) so that there is at least half wavelength between PML and PC cavity. You will also need a finer mesh to make sure that you are resolving holes properly.

Please keep me updated with modified simulation file and results and I will be happy to be of a help.



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