Menu

Discussion Forum

New Discussion
Filtern

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Instability when modelling gold in the wave optics transient model

Posted 27.02.2025, 15:19 MEZ Electromagnetics, Wave Optics, Studies & Solvers 3 Replies

Alan Bowman
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Dear COMSOL Forum

I am trying to simulate a gaussian pulse incident on a gold surface using the wave optics transient model. I created a model based on this tutorial: https://www.comsol.com/model/second-harmonic-generation-of-a-gaussian-beam-wave-optics-14701 and then added a material in the second half of the domain. As the wave optics transient model only uses the real part of the permittivity, I am inputting the imaginary part via a conductivity value instead. When I put in permittivity/conductivity values for a semiconductor the simulation runs well, showing a reflected and transmitted beam with the transmitted being slowly absorbed with distance. However, when I put in permittivity/conductivity values for gold the simulation initially runs, but then the electric field in the gold region becomes unstable - in some small region (and before the beam reaches the surface) the electric field strength rapidly goes to infinity and the simulation crashes. I have tried reducing the mesh size and timestep significantly, but this seems not to resolve the problem. Would someone be able to suggest a method to solve this?

Many thanks in advance.

Best wishes,

Alan

3 Replies Last Post 28.02.2025, 12:24 MEZ
Ulf Olin COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 6 months ago 27.02.2025, 16:36 MEZ
Updated: 6 months ago 27.02.2025, 16:37 MEZ

Hi Alan, I split the domain in the SHG model you referred to and added Gold to the second half (with a conductivity of 45.6e6[S/m]). Compared to the original model, I made no other changes. In my simulation, everything worked. The Gaussian pulse was almost completely reflected, as expected. So, I could not reproduce the instability that you experienced. I suggest that you contact COMSOL support and let them take a look at your model. Best regards, Ulf Olin

Hi Alan, I split the domain in the SHG model you referred to and added Gold to the second half (with a conductivity of 45.6e6[S/m]). Compared to the original model, I made no other changes. In my simulation, everything worked. The Gaussian pulse was almost completely reflected, as expected. So, I could not reproduce the instability that you experienced. I suggest that you contact COMSOL support and let them take a look at your model. Best regards, Ulf Olin
Alan Bowman
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 6 months ago 27.02.2025, 19:09 MEZ

Hi Ulf, many thanks for the message. Did you also update the real permittivity of gold? In case its useful I'm using a wavelength of 1030 nm, here its value is -44 roughly.

Best wishes, Alan

Hi Ulf, many thanks for the message. Did you also update the real permittivity of gold? In case its useful I'm using a wavelength of 1030 nm, here its value is -44 roughly. Best wishes, Alan
Alan Bowman
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 6 months ago 28.02.2025, 12:24 MEZ

P.S. At 1030nm I believe the conductivity of gold is about 32000[S/m]?

P.S. At 1030nm I believe the conductivity of gold is about 32000[S/m]?

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content