2D modal_volume_in_box approximation for modal volume

[Creamyweenie20]

Hello Everyone,

I am trying to obtain the Purcell factor for a 2d simulation I am running for a photonic crystal. To do so, i am using the modal_volume_in_box function with my 2d computation cell. I was a bit confused over the units, however, since I am using the standard definition of the Purcell factor, and it seems like the function might be returning the modal volume in units of the characteristic length squared.

My question is: what units would the modal_volume_in_box be returning in this case?