Should mount the lasers on the spacecraft itself. Laser light travels at the speed of light for any observer, so where it is sourced is immaterial. Then, braking is a non-issue, with a turning maneuver about half-way.
If you did that, then you'd have to also accelerate the mass of the laser(s) AND the power plant in addition to the spacecraft itself... which would reduce the amount of acceleration for the given amount of power input.