source intensity of vertical waveguide photodetectors

Dear community,

I am using FDTD Lumerical. In the example

The source intensity in the analysis of “Generation_rate” is 6.66667E10.

I want to know how to get the source intensity, because the source intensity is important when calculation responsivity.

Another question is that when I change the geometry of WG or PD, does the source intensity change? If yes. How do I get the source intensity?

Thank you very much.

Chun-Ti Lu

Hi @d01941013

In CW normalization (which is the case in this example), the source intensity has units of watts/m^2. Since the output source intensity is assumed to be 1 W and ModeSource has a geometry of 10 um * 1.5 um, the output intensity would be 6.67e10.

If you want to calculate the actual source intensity in your simulation, you can use sourceintensity(f) (where f is the frequency of interest) command. This is used in analysis group to normalize the 6.67e10 to actual emitted source intensity.

Sourceintensity(f) should return you the emitted intensity. This value depends on the source size and bandwidth, but should be indepenpendent of the WG geometry (I didn’t understand what PD means).

I hope this explains how we got 6.67e10 value and how you can calculate source intensity in your simulation file.