most modern garage door openers turn on the light again if you pass through the beam even if the door has been open for a while. If this were me, I'd unscrew the lighbulb in the GDO and plug a socket to plug adapter in there - and power the laser off that. I also don't personally use the lights in the garage door opener - I use the contact sensors on all the doors to turn on the fluorescents - much brighter. That would accomplish having the beam on only when you want it, and turn it on again if the door has been open for a while then she drives in.