While very inefficient, the use of a slit could replace a cyl lens. As you close the gap, Heisenberg requires the momentum to become more and more uncertain as we restrain the position by the gap. That makes the beam expand relative to the slit. If you focus on the slit you can minimize the wasted energy, spread the beam, and spatial filter all at once. So by placing the slowest expanding axis in line either the slit which is best anyways, the beam should expand in that axis. Adjust the slit to adjust the expansion to match the other axis. I tried this and it does work. My problem was extreme power loss but I had not tried focusing the beam on the slit. The effect is based on the slit width not the beam width so you should be able to pass most of the beam by focusing. I didn’t look at what that does to polarization.