Use a lot of very small retroreflectors on your hull.
A retroreflector is a special type of construct that enables incoming light to be sent back to the overall direction of the source with minimal scaterring.
If your enemy fires a laser into your direction and it hits a retroreflector, he is firing back into his own laser cannon - he will do some damage to you in the process, sure, but in the end his weapons will be taken out of comission in a very explosive way almost at the same instant they fire it.
This has the advantage of instant retribution - hopefully, his lasers won't be able to fire long enough to damage your hull but will fire long enough to destroy themselves. Lasers are delicate things, and probably won't withstand the extra energy being pumped back at them in this sudden manner.