But first: pulse lasers bite. This was done with the appropriate safety goggles. And, lets not use the "good" mirrors. (they are about 6 inches square.) My "good" beam splitter is a polarizing cube, so its actually rated for pulse lasers, but instead I used a convenient beam splitter which doesn't have all the 1/2 wave plates attached to it. In hind-sight, I should have used a piece of Plexiglas or something... The laser gnawed a hole in my beam splitter. And do not use microscope objectives, they are put together with optical cement, which will turn black. (I have also empirically observed that effect...)
So, assemble the usual interferometer. Beam splitter at the upper right corner, right by the laser, arms going to upper left and lower right corners, and extra steering mirror by the beam splitter to put the beam diagonally across the table to a lens on the lower left corner to expand it and hit the projection screen.
There are a bunch of unused optics still on the table. I didn't want to deal with moving them... (The beam from the interferometer is actually going through the middle of a plate holder... The paper on the lower left corner is an aperture to block light which was going approximately parallel to the beam, but missed the (also obscured) lens. The interference pattern was projected onto a box off camera to the lower left.
The length of the arms was 23 inches, and the same length within an inch. (My tape measure is not the pinacle of accuracy.)
And after all that setup, the result was a resounding negative. The two beams converged on the screen, and formed absolutely no pattern. The laser must be extremely multi-mode. Dan had a good point later, that the laser's polarization may have wrong, and prevented the interference, but I have not investigated that hypothesis yet.
The other result was the laser mangling my beam splitter...
Note the crescent shaped burn in the middle of the cube. Thus the big lesson: even if its a small (10 millijoules/pulse) pulse laser, it will eat sputtered metal optics.