Theoretical round multimode "dot"

Please praise my amazing paint skillz!

Anyway, here is what I was thinking. Nobody likes a c-mount because they are a PITA to get a nice beam and dot with, but what if you had a FAC c-mount diode and you focused the square beam through a round hole a little bit smaller than the square beam. A little power would be lost because 4 corners of the square beam would be lost on the back of the hole, but you should get a nice round beam after that, right?

Has anybody tried this? It would be nice to use those 1W red diodes in a portable host while still having a standard "round" beam!

Also, another quick question. A c-mount is half hetsink, right? What if you were to file down the corners around the set screw hole.(see pic) Then you could fit the diode closer to the side of a host and still have the beam exiting out of the middle of the host. I would assume it would be safe if you shorted the terminals for static reasons and covered the actual laser part of the mount.

Any thoughts?

I dont think it will work well. You will definitely get artifacts from the beam grazing the round aperture, probably resulting in something worse than the square-ish beam you started out with.

You can easily circularize the output of a multimode diode by coupling it into a short piece of singlemode optical fiber. The fiber output will be perfectly round with almost perfectly flat power distribution across the beam.

Regarding your c-mount idea, it could work but I wouldn't recommend filling that much metal way from a working c-mount as it won't work afterwords. They make half-size c-mounts that aren't square but rectangular as if the bottom half had been cut away.