Prerequisites:

Description:

    This is the technique of using an (electric or similar) power supply to power a laser at the back side of your vessel to push your ship forward.  (Yes, light does have a momentum, it just isn't very much for ordinary amounts of light).  Since this technique is so very inefficient, it probably isn't a good idea unless you have a really powerful power supply technology available.
    For any power supply technology less efficient than fusion this probably isn't worth carrying at all.  For fusion or antimatter, a laser rocket system will be less directly effective than simply using the associated rocket technology.  The power in that case is that every ship will have a very substantial minimum weapons system (the laser rocket itself).  By building so very many and very powerful laser systems, the necessary development into lasers will happen to develop them as weapons far faster than a civilization that is not building so many of them.
    For zero-point or other "free" energy technologies, laser rocketry makes perfect sense.  It is the ideal method of propeling the ship, given the power available.