I have always wondered why the new 40w module from NEJE cost more than twice that of the 30w module, when the 20w module is only about $10 cheaper than the 30w module.  Well I was poking through the neje.shop website and came across a video where they disassemble the laser.  

It turns out that they are using two laser diodes with a beam splitter to combine the output back together.  That makes it plausible that they are getting 15w out of the diodes, assuming the diodes were 6w and overdriven by 20% or so.

I also painted my bed mat black to reduce the flashback and make things a bit more safe.  It works better than I would have though.  We will see how long the paint lasts but I think it was worth the effort.