I am trying to use FDTD to simulate a cavity surrounded by two bragg gratings. The design is basically a core of a silica fiber ( diameter 2 micron) in which the grating and the cavity are etched.
First I wanted to check the behavior of the grating, so I simulated 20 periods of 1 micron depth, 808.3 nm width, the period is set to 202 nm with a silica length of 127nm.
The results I get strange results such as a transmission above 1, and the reflection spectrum does not fit a Bragg mirror spectrum, as you can see on the following picture:
Here is the file I made :
BraggGrating - 20 periods.fsp (6.2 MB)
I tried different meshes and several parameters in fdtd but I still get similar results.
Can somebody advice me ?