Why absorbed power greater than 1?

fdtd

#1

Above shows the absorbed power of my desired design which consists of micropillars. The absorbed power is greater than 1. I think it’s not a right answer as the summation of reflection, transmission and absorption should be 1. What is the issue here?


#2

It is possible that continuous reflections within the substrate and from the substrate=air interfaces are causing superpositions. Monitors are not able to distinguish this from the actual transmission, and cmay be causing the overall value to be greater than 1.

Can you upload the simulation file, and the script file that you used?


#3

I am sorry. Actually I don’t want to share the simulation file. Sorry about that.

I didn’t use any script. I used solar analysis group to observe the Pa s_total and obtained this absorbed power.

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18[quote=“1130344, post:2, topic:17045, full:true”]
It is possible that continuous reflections within the substrate and from the substrate=air interfaces are causing superpositions. Monitors are not able to distinguish this from the actual transmission, and cmay be causing the overall value to be greater than 1.


#4

Hi @sbs019

Other than the fact that the reflection from the material interfaces cause reflection and thus transmission above 1, you also need to modify the simulation file if its necessary. Unfortunately I do not have access to your simulation file but please check the followings:

1, Make sure that simulation triggers auto shutoff level.
2. Leave at least half the wavelength between edge of your objects and PML boundaries.
3. Use different PML settings and make sure that light is absorbed by PML.

As always, perform convergence testing to make sure that results are reliable:
https://kb.lumerical.com/en/layout_analysis_test_convergence_fdtd.html