(written from a Production point of view)
Nolan first began his association with Star Trek, when he portrayed an Enaran cadet in the episode "Remember" in 1996. Soon after this he was cast to work as photo double for actor Robert Duncan McNeill and portrayed a regular command division ensign throughout the last five seasons of VOY.
He continued his work on Voyager as a holographic Irishman in the episodes "Fair Haven" and "Spirit Folk". At one point the holographic characters capture Paris and Harry Kim with a fishing net, the only scene to show McNeill with his doppelganger.
Nolan also portrayed MACO R. Azar several times, featured prominently in the Star Trek: Enterprise episode "Borderland". His costume from this episode was sold off on the It's A Wrap! sale and auction on eBay. The same costume and name tag was also worn by background actors Jorge Benevides and Chase Kim and stunt actor Shawn Crowder. 
Outside Star Trek, Nolan worked as background alien on the science fiction series Babylon 5, which starred Bill Mumy, Patricia Tallman, and Andreas Katsulas and on the science fiction comedy Galaxy Quest (1998).