bjornsturmberg / NumBAT

NumBAT, the Numerical Brillouin Analysis Tool, integrates electromagnetic and acoustic mode solvers to calculate the interactions of optical and acoustic waves in waveguides.
GNU General Public License v3.0
17 stars 13 forks source link

Acoustic modes are incorrect for leaky waveguides #10

Open thariq-shanavas opened 1 year ago

thariq-shanavas commented 1 year ago

I am trying to simulate a leaky acoustic waveguide for forward SBS, where a significant fraction of phonons are expected to leak into the substrate. COMSOL simulations suggest that the acoustic quality factor of the waveguide is expected to be around 500 to 1000 taking into account only the phonons lost to the substrate. It would probably be in the 200 to 500 range if material absorption is also considered.

The calculated acoustic modes are incorrect because the acoustic waves are reflected back from the boundary of the simulation. (As mentioned in Literature example 4). What would be the best way to work around this?

I am aware the main fork of NumBAT is at https://github.com/michaeljsteel/NumBAT, but that repo does not permit raising issues. Thank you so much for the time and effort that went into building this software package, and making it open source!

cc @michaeljsteel

michaeljsteel commented 1 year ago

Hi Thariq,

Yeah, no doubt this is a problem. The absence of open boundaries/PML in numbat is the biggest missing feature and presents real challenges for certain structures. I would like to get this added but it's a far from trivial task and I don't currently have a student keen or capable of doing this.

It's something that is proving a problem for us at times, so I'm definitely pushing towards making it happen, but can't promise anything in the short to medium term.

Incidentally, I've now turned on Issues in my repo.

I'm glad NumBAT is proving useful, notwithstanding the leaky modes problem. If you haven't updated to the current tree you'll find a lot of improvements in usability I think. There are few API change to deal with, but it's worth it.

Best wishes Mike


Professor Michael Steel (he/him)

Professor of Physics Faculty Academic Lead (Diversity, Inclusion and Belonging)

School of Mathematical and Physical Sciences Faculty of Science and Engineering | 12 Wallys Walk, Rm 413 Wallumattagal Campus Macquarie University, NSW 2109, Australia

W: http://physics.mq.edu.au/~msteel/ M: (+61) 0434 631 757

I work on the unceded lands of the Wallumattagal and Cammeraygal peoples.

[allylogo]

[Macquarie University]http://mq.edu.au/

CRICOS Provider Number 00002J. Think before you print. Please consider the environment before printing this email.

This message is intended for the addressee named and may contain confidential information. If you are not the intended recipient, please delete it and notify the sender. Views expressed in this message are those of the individual sender, and are not necessarily the views of Macquarie University.


From: Thariq Shanavas @.> Sent: Friday, 27 October 2023 6:50 AM To: bjornsturmberg/NumBAT @.> Cc: Michael Steel @.>; Mention @.> Subject: [bjornsturmberg/NumBAT] Acoustic modes are incorrect for leaky waveguides (Issue #10)

I am trying to simulate a leaky acoustic waveguide for forward SBS, where a significant fraction of phonons are expected to leak into the substrate. COMSOL simulations suggest that the acoustic quality factor of the waveguide is expected to be around 500 to 1000 taking into account only the phonons lost to the substrate. It would probably be in the 200 to 500 range if material absorption is also considered.

The calculated acoustic modes are incorrect because the acoustic waves are reflected back from the boundary of the simulation. (As mentioned in Literature example 4). What would be the best way to work around this?

I am aware the main fork of NumBAT is at https://github.com/michaeljsteel/NumBAT, but that repo does not permit raising issues. Thank you so much for the time and effort that went into building this software package, and making it open source!

cc @michaeljsteelhttps://github.com/michaeljsteel

— Reply to this email directly, view it on GitHubhttps://github.com/bjornsturmberg/NumBAT/issues/10, or unsubscribehttps://github.com/notifications/unsubscribe-auth/AGIAAPD6K632E4ZRQFFCMO3YBK5G5AVCNFSM6AAAAAA6RX3V6GVHI2DSMVQWIX3LMV43ASLTON2WKOZRHE3DIMRWHEYDANQ. You are receiving this because you were mentioned.