there are several ways of creating the effect of a laser beam.
I know a few of them for example,
start with adding a dark collar with big soft brush(outside of laser)
then painting over with a smaller brush with a lighter collar until you reach a white collar.
(all on the same layer)

or

just create a soft brush white line and add in a glow layer style.

and there are a few other methods.

so what method do you use and of course why?