-
-
September 19, 2023 at 10:51 pm
Seyed Mohammadhossein Enjaviarsanjan
SubscriberHello there,
I am working on the 1D photonic crystal which I expect to show a quality factor of about 1 million. I used the high q analyzer embedded in Lumerical FDTD.
I recently found out that the quality factor changes using changing frequency points in the global properties of the "monitors" section in the software.
So I simulate my cavity considering random dipole in the region to excite the resonant modes, I am using this method to find the intrinsic quality factor of my structure.
As far as I know, the time monitor which is used in this method to calculate the decay of energy from the cavity is not dependent on the number of frequency points, right?
Would you please guide me, so I can make sure that my simulation is reliable? -
September 20, 2023 at 5:53 pm
Guilin Sun
Ansys EmployeeThe number of frequency points is to output how many resonant wavelengths.
Does the change happen to the largest Q? did you check the resonant wavelength?
For such devices if the periodicity does not change but only hole diameters change, you will make sure each period has exactly the same mesh, eg, you will need an override region with mesh size delta=period/N where N is an integer. However when both the diameter and peioidicity change it is challenge to have integer number of meshes. In this case you may need to use finer mesh along the direction of local periodicity.
-
September 20, 2023 at 6:26 pm
Seyed Mohammadhossein Enjaviarsanjan
SubscriberSo I use auto-nonuniform mesh 3. For the same structure(all of the parameters are exactly the same except for a number of frequency points), the highest quality factor changes dramatically.
But the wavelength of resonance doesn't change that much(less than 1 nm -- resonance wavelength is 775 nm)
This is the highest Q which is my desired one.
I can not realize how this number can change the quality factor since the time monitor does not have any input related to that.
Is it related to the post-processing of calculating the quality factor?
Also, I created a defect using different distances between holes in the cavity region and I kept the diameter fixed.
just for your kind information even with mesh 3, the quality factor is about 1M, and finer mesh size doesn't change the resonance wavelength.
It just increases the Q. -
September 27, 2023 at 12:21 pm
Muhammad Danial Haziq Azizan
SubscriberHye,
Can I get your files cause I am stuck on doing that? My Q factor changes if I change the source. I do not really understand about this. Really need help. Here is my email. (md.haziq@graduate.utm.my)
-
September 27, 2023 at 3:52 pm
Guilin Sun
Ansys EmployeeIt meeds careful meshing and selecting the time widow for post processing.
The uniform mesh is to guarantee the periodicity. Without proper periodicity the result might deviate the theory. Please note that the discrete mesh matters for the simulation.
As far as 2008 Harvard team reported over 1M Q factor for Photonic crystal cavity so high Q is not an issue for Lumerical FDTD.
Once the meshing is proper, both the dipole sources and the time monitors can be modified to be placed where the field intensity is strongest for around the desired wavelength. You can place one or more profile monitors to record the fields with much longer simulation time than Q simulation, with apodization setting:
https://optics.ansys.com/hc/en-us/articles/360034902473-Understanding-time-apodization-in-frequency-domain-monitors
Thus it will be iterative: get rough resonant wavelength and Q, modify the locatios of the dipoles and time monitors, simulate Q again,... when the mesh is proper. Please note in the two cases the simulation time can be very different.
-
September 27, 2023 at 3:58 pm
Muhammad Danial Haziq Azizan
SubscriberCan you share it file? my result for FHWN is around 1.2. It is to large and make qfactor value is low.
-
September 27, 2023 at 4:05 pm
Guilin Sun
Ansys EmployeePlease visit online examples as we are not allowed to share any files.
https://optics.ansys.com/hc/en-us/articles/360041567754-Photonic-crystal-cavity
https://optics.ansys.com/hc/en-us/articles/1500006350801-Tips-for-simulating-high-Q-Photonic-Crystal-PhC-Cavity
https://optics.ansys.com/hc/en-us/articles/360042088453-Bragg-microcavity
You can also invite peers in the feed for a specific topic.
-
September 27, 2023 at 4:11 pm
Muhammad Danial Haziq Azizan
SubscriberI dont have member to discuss in my area. I am doing alone my research because in my department, only me use this software.
-
- 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.

Ansys Blog
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
-
7742
-
4502
-
2961
-
1449
-
1322
© 2023 Copyright ANSYS, Inc. All rights reserved.