Dear Ardavan,
Thank you very much for your explanation and clarification. Best, Liang ________________________________ From: Ardavan Oskooi <ardavan.osk...@gmail.com> Sent: Sunday, August 29, 2021 5:47 PM To: Liang Chen; meep-discuss@ab-initio.mit.edu Cc: cq.chenli...@gmail.com Subject: Re: [Meep-discuss] Instantaneous space-time-dependent absorbed power density in a lossy material To compute the time-dependent absorbed power density is straightforward: you would need to manually compute the dot product of the complex conjugate of E and dP/dt by using P=D-E. You can obtain the time-dependent E and D fields using the `get_array` function: https://meep.readthedocs.io/en/latest/Python_User_Interface/#array-slices<https://urldefense.com/v3/__https://meep.readthedocs.io/en/latest/Python_User_Interface/*array-slices__;Iw!!Nmw4Hv0!jt0G2d3ZLlG7sYXPOgib2kMX4_p7Nikvb7BjDfjbcUBn8IqwHuAL7Lmi-5yBcPyLSrcD$>. Note though that the fields obtained using `get_array` are interpolated to the center of each Yee grid voxel which means there will be some discretization error when computing this dot product. (This discretization can be reduced by increasing the grid resolution.) Also, you will need to be careful about the finite-difference approximation you use to compute the derivative dP/dt to ensure that all the quantities used to evaluate the dot product are at the same time instant. On 8/29/21 07:23, Liang Chen wrote: "I realize that MEEP can calculate the absorbed power density distribution (space-dependent) corresponding to each frequency component of a pulse. This is explained in the tutorial "absorbed power density map of a lossy cylinder." However, the problem I have on hand requires the space-time-dependent absorbed power density since the instantaneous absorption is expected to change the material properties, which will then affect the propagation of electromagnetic fields (i.e., it is nonlinear, and using Fourier transform after the simulation is not correct for this problem). If I could get the instantaneous absorption, I can add the feedback mechanism in the MEEP code."
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