I am trying to simulate light incident on a semiconductor sample underneath an AFM tip. The AFM tip has micron-scale dimensions, so diffraction will occur. I have created a CAD model of the AFM tip in Solidworks and imported it into Zemax as an STL file. I am not sure how to set up my Zemax project to calculate diffraction around the AFM tip. I would appreciate it if someone could point me in the right direction.

The CAD model and Zemax project are attached here.

Thank you!