June 17, 2021 at 2:41 amRui_XuSubscriber
I am trying to simulate the behaviour of Fabry Perot cavity in THz region made by two Au mirrors. I start with the simplest situation, which is just two Au thin film with vaccum inside (attached file). The dielectric functions of Au in THz region is described by Drude model, which is Plasma in the database. The distance of two thin films are 7.5um, which corresponds to resonance at 15um. However, the result of reflection spectra just looks weird (attached file). Can anyone help me solve the problem? Thanks!
RuiJune 17, 2021 at 5:05 pmGuilin SunAnsys EmployeeHi, Rui, Ansys employees are not allowed to download ALF posts from customers. Maybe you can give some screenshots.
In THz usually it needs much longer simulation time than the default 1000fs. You may try 10~100ps or even longer. Please check this Chinese posts: Ansys Insight: Õªéõ¢òþƒÑÚüôFDTDþÜäõ╗┐þ£ƒµùÂÚù┤ÞÂ│ÕñƒÚò┐
In addition, you will need to set periodic BCs perpendicualar to the light propagation and use sufficient thick PML along the light propagation. Please try to modify the settings. In addition, you can add a time monitor and check the signal if it decays completely.
June 17, 2021 at 5:39 pmRui_XuSubscriberHi gsun Thanks for the quick respince!
Here are some screenshots which may be helpful. I used anti-symmetric BC perpendicular to light propagation orientation and standard PML along (fig 1). The reflction spectra is smooth but just wierd, even over 1 at some points (fig2). The time limit I set was 25000fs, but the simulation autoshut off just at 2500fs. The time monitor at the center of the cavity is shown in fig 3. Seems there is still a little field. Does it mean I need to decrease the auto shutoff to be smaller than 1e-5?
June 17, 2021 at 7:09 pmGuilin SunAnsys Employeeyes, try 1e-6 or1e-7. Make sure the simulation does not terminate at 100%.
June 17, 2021 at 7:53 pmJune 17, 2021 at 9:07 pmGuilin SunAnsys EmployeeThe time monitor still shows strong signal, so smaller autoshutoff is further needed. You can try 1e-9 and longer simulation time. At the same time, make sure the PML has about half wavelength thick, which you can roughly measure it using the ruler in the left-hand panel. Since you are using Au material as mirrors, the reflectivity is very high, so the signal can be decay very slow and there is no other mechanism such as higher diffraction orders to leak energy.
I suggest that you monitor the transmission. You can also move the reflection monitor in between the source and the mirror to get the reflection. Please refer this post Ansys Insight: Õªéµ×£ÕÅìÕ░äþøæÞºåÕÖ¿õ¢ìõ║ÄÕàëµ║Éõ©Äþ╗ôµ×äõ╣ïÚù┤Õªéõ¢òÕ¥ùÕê░µ¡úþí«þÜäÕÅìÕ░äþÄç
June 17, 2021 at 10:29 pmRui_XuSubscriberThanks for the suggestion!
Now the time signal has been decayed to ~1e-5, and the thickness of PML is larger than half of the wavelength. The reflection spectra are all smaller than 1, though still looks interesting. It is supposed to be a dip at ~15.6um, somehow half of it just inversed. Is it due to the meshing problem? Since I just meshed the region where the Au mirror is.
June 18, 2021 at 12:09 amGuilin SunAnsys EmployeeWhat is the thickness of the mirror? does the time monitor show the complete signal ? if so, the signal is still strong. The DFT monitor cannot get accurate result because of the signal truncation. Please make sure the autoshutoff level is small enough and the simulation time is long enough and it terminates at less than 100% in the progress.
If there is still problem, please give me all the device parameters so I can have a test if I have the time.
June 19, 2021 at 5:32 pmRui_XuSubscriberHi gsun The thickness I used is 50nm, and the distance between the two are vaccum with T=7.8um. The dielectric function I used for Au is plasma model, with epsilon=6.88, resonance frequency= 8.96eV, gamma=0.0723eV. The light source is just plane wave from 10-20um, since the resonance should be @15.6um. Anti-symmetric BC are used in both x boundaries. Could you please have a try if you have time? Thanks a lot! If additional parameters are needed please let me know.
Viewing 8 reply threads
Ansys Innovation Space
- You must be logged in to reply to this topic.
Simulation World 2022
Check out more than 70 different sessions now available on demand. Get inspired as you hear from visionary companies, leading researchers and educators from around the globe on a variety of topics from life-saving improvements in healthcare, to bold new realities of space travel. Take a leap of certainty and check out a session today here.
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.Trending discussions
- “Import optical generation” or “delta generation rate”?
- Why am I getting “process exited without calling finalize”, and how do I fix it?
- Error on Lumerical device
- Using a license file on a new license server
- Ansys Insight: Diverging Simulations
- Ansys Insight: About override mesh in FDTD: its use and settings
- Error: addfdtd is not a valid function or a variable name
- Ansys Insight: Transmission results greater than one
- Ansys Insight: Convergence issues in CHARGE
- Is there a Lumerical script command to output the Simulation and Memory requirements?
Top Rated Tags
© 2022 Copyright ANSYS, Inc. All rights reserved.Ansys does not support the usage of unauthorized Ansys software. Please visit www.ansys.com to obtain an official distribution.