I really don't know much about lasers (other than what I just read on wikipedia), but there are some crucial elements missing. First off, if you've been looking at the info online, it would probably help to take a look again. Here's a brief explanation from
Wikipedia.
So, if I follow this correctly, to break it down into basic elements, you'd first need a highly reflective cavity, although apparently a mirror on each end is sufficient, you don't need a completely sealed chamber. At least, that's what I got from the reading. You'd also need a gain medium in the center, which is apparently something that, when energized, amplifies the light of a specific wavelength. Crystals can be used for this but they also mention gases, and from what little I've heard, I think those are more common. The light source is external and apparently just requires a fairly intense source, since they specify a flash lamp in the description. I'd think a flashlight or regular bulb would be too dim. One of the mirrors apparently has to be semi-transparent for the laser to come out one end. There's a picture next to the section that I linked to that describes the basics pretty well.
All this being said, it seems that the entire process is extremely precise, it's definitely nothing like just bouncing a light around inside a chamber with a bunch of mirrors. I would imagine you'd have to calibrate the medium exactly for the wavelength you want. It's really not the type of thing that I think somebody could just throw together without a lot of technical study.
