Split ring resonator Tranmission


#1

Hi,

I am new to lumerical and as start I was trying to simulate what already exist. I used the model based on the paper
https://www.osapublishing.org/josab/abstract.cfm?uri=josab-26-12-b143

My program is attached along with this. I tried with Aluminium and PEC without much success. Parameters like mesh size, frequency,bandwidth,Boundary condition(between pml and symmetric) all were changed and tried but none of them are giving the desired result. Is this a problem with lumerical?

Also while trying to simulate with Al Palik, I am getting engine failure.

Thank youresonator1.fsp (248.2 KB)


#2

Hi,
Would you please upload a file with “Ag- Palik” ? I believe the perfect conductor won’t support the plasmonic resonance modes we are supposed to see.

I recommend you have a look on this thread:

The Bull’s Eye aperture example below is very close to what you want to do. Let is be your starting point. Then replace the circles with your squares and change the wavelength range. Keep me updated on what you get.

https://kb.lumerical.com/en/sp_bullseye_aperture.html


#3

Hi,
This is just an update
I am trying to get Tranmission dips around 0.5,1.6 based on TE or TM mode. I have taken into account the minimum distances between monitor and source, made sure CV1 is used, antisymmetric boundary condition in x, periodic in Y and PML in z. I am getting dips near 1 and 0.4 for TE and 1.6 for TM, I am not even sure they are the actual dips as its too noisy. Also when I increase the simulation time to decrease the noise, I am getting different behavior. May be these questions might answer my problem.

1)Why do responses at particular frequency changes with bandwidth? In this case how will I decide my bandwidth?
2) Can symmetric antisymmetric conditions be kept in oblique incidences or should I keep PML?
3) Why does some times simulation diverge with change in bandwidth?
4) Why is transmission coming negative even when my direction of propagation is forward?

I wonder whether I am making any ignorant mistakes.

Thank you


#4

Would you please attach some figures? I am not quite following your problem.


#6

Hi,

I am adding pictures for clarifications. This is my program file.resonator1.fsp (251.3 KB)

  1. Transmission data when I change nothing but bandwidth.
    0.1 to 5 THz-

0.1 to 10 THz

Why does the behaviour at one particular frequency change with bandwidth?

  1. I realised this problem is also not there all the time. Its there some time and some time it just works. Even if it shows engine failure running it again makes it work.

  2. The propagation direction is positive in the setup but still some part of the transmission is coming negative. I have no clue why. Here I have just changed the polarization by 90 degrees.


#7

@aya_zaki

1)Why do responses at particular frequency changes with bandwidth? In this case how will I decide my bandwidth?

Here you can see that for the same file for two different bandwidth of the source, I am getting two very different results.

  1. Why does some times simulation diverge with change in bandwidth?
    Some times my simulation is diverging by simply changing the bandwidth. This is not a consistent problem, but for a different structure I realized this happening quite a lot for a particular bandwidth. Some times re running without any change solve it. But some times it never works how many times you run.

  2. Why is transmission coming negative even when my direction of propagation is forward?
    This is the same structure with 90 degree polarization

this is my file resonator1.fsp (251.3 KB)


#8

Dear @ak12ms026

Sorry for the wait.

Based on your figures and after checking your simulation file, it looks like the PML boundaries were too close to device. As a result you are getting reflection from PMLs where their size can vary with wavelength. Generally we recommend everyone to do convergence testing to make sure that the results are stable with changes in the mesh size, FDTD simulation region, and number of PMLs.

I run a few simulations and looks like PECs create some plasmonic effects and the trapped light takes a long time to be dissipated. On the other hand, since PECs are very thin compared to injected light wavelength, simulations take a long time to finish.

Thanks to @fgomez, an alternative approach would be to use 2D PECs. This should be a very good approach to decrease simulation times significantly. Although in some cases we still need to use fine meshes along the material thickness (for 2D material), you can start with no mesh override. Please adjust the PECs and let me know if you encountered any problem.

I have the modified simulation file attached for your future references (since you mentioned that you are new to Lumerical), but please note that you will need to increase the simulation region, adjust the PMLs, and use finer mesh to make sure that your results converge. Generally speaking, these type of simulations that involve plasmonic effects are challenging, and for your case, convergence tests take a long time due to mandatory use of fine mesh resonator1_modified.fsp (254.7 KB).