Various embodiments disclosed relate to an assembly. The assembly includes a compound parabolic concentrator including an exit aperture that has a generally circular perimeter, which defines a circumference of the exit aperture. The assembly further includes a photodiode sensor generally that is aligned with the exit aperture of the compound parabolic concentrator. An optical adhesive layer adheres the exit aperture of the compound parabolic concentrator to the photodiode sensor. A protrusion extends between at least a portion of the perimeter of the compound parabolic concentrator exit aperture and the photodiode.