Well... they are 15mm x 15mm x 15mm and are tuned to the wavelengths better than the cube in the sleds. Also, the larger size means they will hold the beam rather than have the edges spraying out of the sides... and they are meant to be used for combining beams of the same color, while the ones in the sleds (not sure, please correct me if I'm wrong) are for combining different colors or for reflecting the returning beam...
Thanx Daedal! I was wondering about a few of the relevant particulars. :-? Wikipedia was a bit of general refresher, but dimensions, etc. are of real interest.
Without getting into the details of it, you need to have 2 beams at different polarizations from each other to combine them in a PBS. The combined beam is then outputted as the resultant sum of the 2 beams, which will have 2 different polarizations to it now. Adding the output from 2 cubes into a third cube, or inputting the combined beam into another PBS, will net you nothing... Half the beam will be reflected... :-?
Although... you can 'fatten' the beam and combine 4 beams into one using a PBS with some patience and maneuvering as you can see it done here
I bet you I'll get many droolings for that first link I have there... and rightfully so too... ;D My keyboard gets wet every time I see that picture! :-[
Cannot recall my login info to see the pics. So - PLEASE correct me if I am wrong...but without using polarized lasers, these beam combiners won't work ? My Optics education is not up to par with some of you folks, so if someone would care to humiliate me, and my feeble little brain, I would appreciate it !