This video is taken from the varFDTD Learning Track on Ansys Innovation Courses.
This is the simulation file for the silicon-on-insulator taper that we looked at in the previous demo.
Open the Material Explorer from the Check menu.
In the Material dropdown, the core material and 4 test materials listed, since there are
4 test points set up.
There are only 2 unique vertical slab profiles for this device: one with air/silicon/glass,
and another with just air and glass, so we would only need to use the core material and
1 test point to be able to plot the 2 effective materials that will be used in the simulation.
The remaining test points give duplicate information.
Click the “Fit and plot” button to plot the core material's effective index over the
source wavelength range which is between 1.5-1.6 um.
Now plot test material 1.
The material data for both materials is constant over the wavelength range.
Click the "Close" button to close the Material Explorer window.
If I edit the solver region, I can see that the bandwidth is set to “narrowband” which
is why the material dispersion wasn’t included when we plotted the material data.
Set the bandwidth to “broadband” so the material dispersion will be included.
I can also remove the extra test points that provide duplicate material data by reducing
the number of test points to 1.
Now, in the Material Explorer I only see the core material and one test material.
Re-plot the effective index of the core material.
The material is now dispersive over the range, which captures both the dispersion of the
material refractive index and of the vertical slab mode.
This material fit looks good, but you can change the fit parameters if needed.
Tips for modifying material fits can be found in the link below the video.
If I want to look at the raw material data for the Silicon or glass materials of the
structure instead of the effective material properties, I can do this by either removing
the varFDTD solver region, or by making a different solver region active.
For example, I will add an Eigenmode solver region from the Simulation menu so the FDE
solver region is now the active solver.
When I check the Material Explorer, I can see the Silicon and glass materials in the
Material list and I can plot the material data.
It’s a good idea to check the material data of the materials used in the structure before
adding the varFDTD solver region to ensure that the materials have data in the wavelength
range of interest, so that you know that reasonable refractive index values are used in calculating
the effective materials that end up being used in the varFDTD simulation.