- Sep 20, 2013
I would not use a PBS cube with mirrors attached to it. You want the mirrors to be out several inches away for the beam splitter and one should be able to be moved. The distance it can be moved away from and towards the beam splitter will tell you the coherence length of your laser. Where the fringe lines appear and where they disappear is directly related to the coherence length of your laser. You need to be able to measure this distance.