Here is a bit more information on what he was thinking before making this laser.  Apparently there were some parts and technical issues to work through:

Believe it or not I have had this system sitting around for years now, but only had it running fairly recently. When I bought the head and power supply, I had no controller to run the PSU. I finally got around to building a controller for the unit but I could not get the system to fire up. I ended up taking it to my genius friend Wilson, a senior at my university studying aviation mechanics, who found a problem in the flashlamp trigger circuit and fixed it up for me.

Thanks for making the video and we’re looking forward to more cool experiments.