Propagation characteristics of hybrid modes supported by metal-low-high index waveguides and bends


I simulate this article but i couldnt reach real part of effective mode index like the neff in this article. my result of simulation is in the following. Could you help me please?
thanks alot
Propagation characteristics of hybrid modes.pdf (1.5 MB)


Hi @behnam.badihi,

Can you share your simulation file so we can have a look?

In the meantime, as a starting point, I would suggest to have a look at this getting started example: plasmonic waveguide. It gives some tips about how to set up such simulation.


Thank you for your reply. I use metal boundray and the size of mesh is 10nm . Im not sure about the dimention of the FDE. i am realy appraciate if you could help me.
plasmonic waveguide1.lms (236.9 KB)


The mesh might be too coarse. I would try with a finer mesh localized around the waveguide. Regarding the size of the FDE region, it should be big enough so the boundaries won’t interact with the tail of the mode. Typically, we want the fields to be very small near the FDE boundaries (for instance, -9dB). You may have to do some testing to find the optimum size and mesh.

Also, when doing a frequency/wavelength sweep, you may want to fit the material data using the multicoefficient model:

From the simulation - FDE page:


(For sampled material data) When MODE Solutions solves for modes, it uses material data that is obtained from a linear interpolation from the closest data points. This means that when a frequency sweep is run, the material data used can be discontinuous in time. This is especially problematic for properties such as dispersion which depends on a second derivative of the refractive index as a function of wavelength.

If you check this option, you can choose to fit two types of materials with a multi-coefficient model. Here are the options that are available when the checkbox is checked:

•Fit sampled materials: By default this is checked. Sampled material data will be fit with a smooth multi-coefficient material model.

•Fit analytic materials: Check this option to fit a multi-coefficient model to the analytic material data. The only reason to fit analytic models with a multi-coefficient model is to compare MODE results with FDTD. FDTD simulations must fit a multi-coefficient model to the analytic data in order to run simulations, but the multi-coefficient model may not be able to fit the analytic model perfectly.

•Wavelength min/max or center/span: Set bandwidth over which to apply the fit.


Hi gbaethge. yes you are right my problem was fit the material. thank alot for your help.