Hi everyone,
Here is an update. I have done some testing using the 3D nanobeam project python code found on the Simpetus website: http://www.simpetus.com/projects.html#meep_cavity I found that, with eps averaging on, harminv would still work when the resolution is at 42. However, harminv would fail when the resolution is increased to 44 (originally 40). Also, the mode field output is completely off. When eps averaging is off, harminv found the mode succesfully though with a lower Q-factor, as well as output the expected mode field profiles. I don't know if this is something to do with eps averaging itself or harminv or even with running the scripts on jupyter notebook with parallel meep. Nonetheless, I have managed to reproduce the results of the reported H1 photonic crystal mode and Q-factor using a sufficiently large cell and high enough resolution with eps averaging turned off. In this sense, I think I can avoid possible issues with eps averaging. I would appreciate it if you could consider the following feature requests: 1) Independent resolution for different axes: For example: resolution_xaxis = 40, resolution_yaxis = 40, resolution_zaxis = 20. Often in my simulations, I could use a low resolution in the z-axis. I t would be great is this feature gets implemented as this would mean reducing time with by setting the resolutions suitably. 2) Cylinder with major and minor axes / an elliptical cylinder Essentially an ellipse with a non-zero height to simulation elliptical air-holes. I will try to implement this using the prism function for now. Thank you very much. Best regards, Chee ________________________________ From: meep-discuss <[email protected]> on behalf of Chee Fai <[email protected]> Sent: Monday, November 5, 2018 9:38 PM To: [email protected] Subject: [Meep-discuss] EPS averaging affecting harminv mode search and mode distribution Dear all, I started using MEEP about 2 weeks ago and have been doing some test calculations on MEEP, mainly to reproduce results of cavity mode and Q factors of a H1 photonic crystal cavity as reported in this paper: https://www.osapublishing.org/oe/abstract.cfm?uri=oe-20-27-28292 When EPS averaging is off, harminv could find the modes and the Q values. The mode frequency changes quite significantly with resolution and it doesn't quite converge to the right value but it finds the correct modes i.e. the modes have the expected field distributions. Overall, despite the deviation in the mode frequency and Q values, it works fairly well in finding the modes. However, when I turn EPS averaging on, harminv could find the mode with the correct frequency and Q value but only for certain resolutions. The mode is lost somehow when I increase the resolution. Not only that, the mode distribution is totally off when averaging is on. Note: - I check the mode distribution by creating h5 output files over 1 wavelength to create PNG and gifs as it was done in the tutorial. I don't think this is the problem but I am going to try changing a method to create outputs of field distribution - I perform harminv on Ex, Ey and Hz, all at the same non-zero position, away from points/lines of symmetry. I have checked that the x, y and z symmetry that I applied are correct for the structure and the source. I have also tried to see what happens when I change the excitation bandwidth and/or simulation stop time but I didn't really see a trend that points to the problem of what could affect harminv and the mode distribution. I have also checked the archive to see if others have faced similar problems. Alas, I am here. I hope someone can point to the solution or a direction on how to solve this issue. Thank you very much. Best, Chee P.S. I can attach my code if it helps.
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