Those beams look pretty digitally enhanced to me... But if you want a "physically correct" way, make a super direct light inside of a tube and use volumetric lighting
– LinguiniOct 24 '18 at 19:16
5
See https://blender.stackexchange.com/questions/53548/using-nodes-for-laser-line and https://blender.stackexchange.com/questions/1096/making-a-laser-in-cycles-straight-beam-of-light
– batFINGEROct 24 '18 at 19:20