Among would be the conventional usage here. You can also use between according to Oxford English Dictionary.
To answer your question it doesn't really matter. However if you want it to be clear that there are more than two lasers, use among.
http://grammar.about.com/od/alightersideofwriting/a/Among-And-Between.htm
In general, between applies to reciprocal arrangements (one member to another member), and among applies to collective arrangements (with all members involved). However, as explained in the Oxford English Dictionary and in the usage notes below, between may apply to more than two members.
Edit answering the second part: offsets because there is more than one laser offset, if there are more than two lasers.