September 2, 2023 at 8:09 pmStanleyLimSubscriber
I am having a problem in reproducing the propagation loss a waveguide using VarFDTD. The result  I am interested in reproducing is as follows:
where the thickness of lithium Niobate (LN) is 300nm, the PMMA waveguide thickness is 500nm, and the silicon thickness is 2 microns. I used VarFDTD to set up this waveguide, and sweep the waveguide width. I would like to reproduce figure (c) result at the wavelength of 1550 nm. Here is my VarFDTD setup:
where i set the waveguide total simulation length to be 200 microns, and two monitors are set in the beginning and at the end of the waveguide to measure the transmission spectra at the beginning (T_begin) and at the end (T_end) of the waveguide. Then, I substracted the T_begin by T_end to extract the propagation loss of the waveguide. This is what I obtained after few attempts:
It seems like the result is upside down compared to Fig.(c), and the magnitude of the propagation loss is off. Could you please point out my mistakes or provide some comments regarding to this issue? Thank you so much in advance.
 Yu, Zejie, et al. "Photonic integrated circuits with bound states in the continuum." Optica 6.10 (2019): 1342-1348.
September 5, 2023 at 2:53 pmDevika Padmakumar NairAnsys Employee
We dont have access to journal papers. Ansys Insight: Ansys Innovation Space —- Forum and Feed
Can you elaborate which tool the author used to calculate propagation loss? MODE or FDTD?
Also which monitor are you using in your simulation?
Thanks and regards
September 5, 2023 at 3:22 pmStanleyLimSubscriber
Thanks for your reply. In the paper, the authors mentioned that one used FDTD to simulate the propagation loss for the waveguide. I used frequency-domain field and power monitor.
September 5, 2023 at 3:53 pmDevika Padmakumar NairAnsys Employee
Thanks for additional information.
DFT monitors will record the power propagating through them. This will not necessarily reflect the actual loss, mainly bcz part of the power will not be in the waveguide's mode.
I would suggest to use a mode expansion monitor so you can get the actual coupling to the mode supported by the waveguide.
Futhermore, I would also suggest to use FDTD to match the results.
Thanks and regards
September 5, 2023 at 6:38 pmDevika Padmakumar NairAnsys Employee
Correction in my previous response, for straight waveguide propagation loss can be calculated simply using FDE. Waveguide (FDE) – Ansys Optics
Also, the post written by Guilin will be helpful.
September 5, 2023 at 11:56 pmStanleyLimSubscriber
My very first attempt is using FDE, but I realized that FDE only takes into accounts of the material's imaginary refractive index (I ran two different simulations, one with actual material parameters with , one with object-defined material parameters without imagnary refractive index). It turns out that the one without imagnary refractive index gave no propagation loss. This is why I used VarFDTD (as the authors mentioned). I will check out more carefully the link you sent me.
- You must be logged in to reply to this topic.
Boost Ansys Fluent Simulations with AWS
Computational Fluid Dynamics (CFD) helps engineers design products in which the flow of fluid components is a significant challenge. These different use cases often require large complex models to solve on a traditional workstation. Click here to join this event to learn how to leverage Ansys Fluids on the cloud, thanks to Ansys Gateway powered by AWS.
Earth Rescue – An Ansys Online Series
The climate crisis is here. But so is the human ingenuity to fight it. Earth Rescue reveals what visionary companies are doing today to engineer radical new ideas in the fight against climate change. Click here to watch the first episode.
Subscribe to the Ansys Blog to get great new content about the power of simulation delivered right to your email on a weekly basis. With content from Ansys experts, partners and customers you will learn about product development advances, thought leadership and trends and tips to better use Ansys tools. Sign up here.
- “Import optical generation” or “delta generation rate”?
- Why am I getting “process exited without calling finalize”, and how do I fix it?
- Using a license file on a new license server
- Ansys Insight: Diverging Simulations
- Error: addfdtd is not a valid function or a variable name
- Questions about the calculation of the cross-polarization conversion efficiency of metasurface
- Error on Lumerical device
- Ansys Insight: About override mesh in FDTD: its use and settings
- Finding your Ansys (or Lumerical) account number
- Lumerical – error message when trying to open from Linux terminal
© 2023 Copyright ANSYS, Inc. All rights reserved.