Open the file "Samples > Physical Optics > Pinhole Aperture.zmx".

This example demonstrates modeling a spatial filter using POP. The lens represented by surfaces 2 and 3 bring light to a focus at the location of surface 4. An aperture is placed on surface 5, which is co-located with surface 4. To see how this aperture is defined, first double-click where it says "Standard" for surface 5 in the Lens Data Editor. Next, click on the "Aperture" tab. A "pinhole" sized circular aperture with a radius of 6 microns has been set on this surface.



The two Physical Optics Propagation windows that open with this file show the beam output before the pinhole (surface 4) and after it (surface 5).

  

The beam has been significantly altered by the pinhole. If the input beam was aberrated, the pinhole would only allow the fundamental mode to transmit, cleaning up the beam. The total power of the beam after the pinhole has been reduced significantly (from the original input of 1 Watt). While the pinhole allowed for beam cleanup, it has also reduced the beam power to 0.18 Watts, less than 20% of the original power!

TIP:  The comment listed in the "Comment" column of the Lens Data Editor will be displayed in the POP window for whichever surface is the "End Surface" defined for the propagation. This can help you to differentiate one POP window from another when generating beam output at different surfaces.