
Originally Posted by
taggalucci
A mirror.
In a simple two beam combiner, one beam direct from the laser passes a 45 degree mirror (very closely). The other laser beam is refelected off the 45 degree mirror as close to the edge as possible ("knife edge" close). This means that the two beams are then side by side. Much care needs to be taken to get the beams to start parallel with each other as well as the angle and position of the mirror to combine without an obvious gap between the beams.
If you look around on the site, you will find 3D diagrams demonstrating this. Spend some time. The information is already here.
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