I am a really new beginner for FDTD. I am trying to simulate 1D PC cavity follow this paper(https://arxiv.org/abs/1108.2675). 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
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.