Send a mirror ahead, bounce the beam back toward the ship to push it backwards. Loses a lot of efficiency, though. Laser propulsion, a lot of the thrust is coming from ablation of the surface.
Yep, throwaway mirror, it goes off to wherever once it's done bouncing light back at your ship. Again, much less efficient, so when you get where you want to go, you'd want to put in a laser station there too.
