Learning Forum

[anshuman.kumar]

Hi

Few queries, as follow

(a) Following this example: https://support.lumerical.com/hc/en-us/articles/360042161033-Fluorescence-enhancement for calculating Purcell factor value of micro-ring cavity geometry. while testing, as I observed in example file that over the change of simulation time (fs) from 75 to 4000 value there is no effect in the nature and magnitude of plot ( decay rate Vs. wavelength, gamma_dipole one). But in my simulation file (geometry) it shows drastic change of gamma_dipole vs. wavelength plot (data from dipole TB box), as you can see in below attached figure, why ? and which one will be correct one?

My file here https://drive.google.com/drive/folders/1XIa6hxfUyNbkpw_ss1NZiwxxSFGSnasd?usp=sharing

[Guilin Sun]

In order to efficiently communicate in ALF, we will need to keep the one-post-one-question policy.
Due to regulations we are not allowed to download your simulation file. However, I can help for the Purcell factor question. When a cavity is involved, simulation time is critical, as the pulse will have infinite number of back and forth in theory. The DFT monitor, and the Purcell factor is a frequency domain result, so it depends on the accurate Fourier Transform, which requires the signal to be decayed completely. Please refer this post: /forum/discussion/25276/simulation-time-and-frequency-domain-monitors
So it is no surprise to me that your result changes with simulation time. Please do a convergence testing with longer simulation time and smaller autoshutoff min.
For mode volume, I did not see any issues. But you may reconsider the physical meaning of the mode volume in the ring, as it is a standing wave inside.
It is normal and physical that the loss is larger in bending case.
Please write new posts for the last two if you still have questions.