Help with simulate Nanoplasmonic MIM filter

Hello.
I’m newbie to FDTD Lumerical. I want to simulate this absolutely simple article: An ultra-compact nanoplasmonic high-pass wavelength filter at telecommunication wavelengths based on a MIM waveguide

The only result to be simulated is “Power Ratio” diagram:
Transmittance%20and%20Reflectance%20spectra

The structure is very simple:

I have simulated the article in FDTD module.:

But after running the simulation, the result has significant difference to the article result:

Now, can anyone please help me and tell me what’s wrong?

I have defined a “Mode Source” with fundamental mode in X-Forward direction.
Used 2-D FDTD simulation with PML Boundary Condition for x-min and x-max and Periodic for y-min and y-max.

I guess my mistake was in choosing the material (Ag Silver Johnson and Christy) which the approximation of FDTD is bad for wavelength 1000(nm) to 2000(nm):

And finally this is my simulation file:
long_pass.fsp (325.3 KB)

Please help me in order to rich the article result.

Thanks.

Hi @xdarem24

Welcome to Lumerical!

You will need to reduce the x-span of FDTD or extend the silver object into PML to avoid the back reflection from the guided section.

Also I am not sure why you used periodic boundaries along y. It should be PML.

You can also use port objects instead of mode source and DFT monitors to inject the mode source and capture transmission:
https://kb.lumerical.com/ref_sim_obj_fdtd_ports.html

Hope this helps.

Hi @bkhanaliloo

I have reduced the x-span of FDTD simulation region to 300 and changed the y-min and y-max boundary condition to PML and increased the layers to its maximum value 64. But the result was diverged.

Now I’m trying to use ports instead of mode sources. I will appreciate if you have another idea to fix this problem.

Thank you compatriot :blush: