Why spend $600 on a 100-Mw laser when you can make one in 10 minutes?
This is a combination of a 'pot mod' (the tightening of that screw) and a 'resistor mod' (soldering iron).
Disclaimer: This modification may shorten the lifespan of your laser pen.
For more info see the comments on digg.com and a detailed article on phalkin.com