I have some pictures on the subject, I believe Arctos holds the patent on this,
here is one of their pictures (I hope this is not illegal to share)
(Arctos 8 Red LASER Combiner - Patent)
Here is a picture up close showing how this is done, It looks like he is using a PBS
(Polarizing Beam Splitter) where one side is at 780nm (like what is used in a dvdrw,
yet a BIGGER cube compared to what I see in the Lite On drive.)
(Obviously this is only joining the power of TWO lasers)
Here (On the left) is a different configuration where both the RED
Lasers are pointing in the same direction, while one is bounced (Left one)
from a mirror into the PBS. After this red is proccessed it goes onto dichroic filters
to finally combine the green and blue
Double the fun for double pleasure
(once you go past combining TWO lasers you cannot literally/coaxially combine more
and you can only do your best at getting the resultant combinations as close to each
other as you can, notice the two seperate beams for an ouput)
And if that isnt enough of a thrill you can always add 48 of them together
(If I recall correctly this guy has a combined RGB output of 35 watts and it is the patent holding Arctos unit)
The patents for this are on the internet somewhere