Sharing this picture, because they are just so pretty.  These are flight-model ruby laser assemblies for the Darkstar laser downlink terminal.  They are not the main communications lasers (nor technically are they ruby lasers), but are low-power metrology lasers used to measure the attitude of the internal fine-steering mirror for realtime control.  The ruby operates simultaneously as an optical lens and as a mechanical pivot point.

Between these, the diamonds in the reaction wheel bearings, and the gold that coats pretty much every surface, this lab feels like a game of Splendor.