This project started one afternoon when I was bored and decided to try to colliminate a red and green laser into a single beam, thus creating a red/yellow/green laser. For more information on the creation process of this and later revisions, check out the forum post I made on 4hv.org.
The first try was about as simple as it gets, just a red laser (extracted from a DVD-R drive, about 80mW of 650nm) and a green laser (extracted from from a laser pointer, about 5mW of 532nm) glued to a piece of aluminum with a red dichroic mirror (salvaged from the DVD-ROM drive) to combine the two beams.
To align it I bolted the block down to an optics bench, and tack glued the mirror to a 5 axis aligner I hacked together from some optical stages I had available:
The end result was quit nice, a golden beam with reasonable divergence that was quite visible at night, and very visible with fog/smoke.
Here is a picture of it reflecting off of a CD-ROM, showing the orange beam coming in from the left and being refracted into its component red/green beams:
Unfortunately, when I took the aligner off of the mirror had drifted slightly, and the beams were no longer collinear. I then realized that in order to keep the beams collinear I would need to have the beams aligned to within +/-.05mrad (~.005degrees) in pitch/yaw, and +/-.01" in x/y/z. The little block of plastic that I had the combiner mirror mounted on just wasn't up for these tolerances, so it was back to the drawing board.
Fortunately, the mixed success of this revision inspired me to improve upon the design to come up with a second revision, this time in full color RGB. Thus was born RGB laser II
I can be contacted at firstname.lastname@example.org