# A Purcell factor in a metallic array

#1

I want to extract a Purcell effect by nanoparticles in a plasmonic array, the structure is similar to a below image.

3D FDTD Solutions model of solar cell device consisting of a periodic array of silver nanoparticles located on the upper surface of the silicon solar cell.

Referring to this KB page, I figured it’s not physically meaningful to apply a dipole source to the plasmonic array with periodic BCs, because the dipole source is also periodically arranged and irradiating in an array manner. What If I applied PML BCs in x/y-axes to the plasmonic device as the suggestion in the page, at least how many particles (unit structure) would be putting into the FDTD simulation box with respect to the incident wavelength of the dipole source? Or is there more simpler method to evaluate the Purcell effect in the plasmonic array?

#2

I’m not aware of any rule of thumb for the number of periods to include in the simulation region, but I would expect that it could depend on the coupling between each period. If the particles are spaced farther apart so there is less coupling between each period then fewer periods of the device would need to be simulated.

I would recommend testing by increasing the number of periods until the Purcell factor no longer changes when you further increase the number of periods. Hopefully this helps!

#3

Hi @nlui,

I appreciate your guideline on evaluating the purcell factor in a periodic structure.
I feel it must be a very useful advice for me.