FDTD custom object issue
I am trying to simulate a logarithmic taper so I have provided the custom object structure two log functions (natural log not base 10), one for the top curve and one for the bottom. The idea is for it to start at x=0 with the bottom curve at y=0 and the top curve at y=0.065 um. At x=65um the bottom curve should be at y=0.065um and the top curve at y=0.257um.
The simulated taper is not being generated as I expect based off the provided equations. It does not start at x=0 which make me think there is a negative issue in the log. However when I plot my functions in Matlab, they behave as expected. I must have some misconception on how this “custom” object needs to be defined.
I have attached the FDTD simulation showing my issue as well as a Matlab plot demonstrating what I am trying to achieve. The blue lines are the linear baseline i.e what the original taper was. and the red line is the desired logarithmic variation.
I am using Lumerical 2021.
Thanks for any help you can provide