The PTO on the front of the F-35 engine has 29,000 hp available. In the A and C models that isn’t driving a lift fan. That could drive a huge generator.
http://www.defenseone.com/technology/2015/09/drones-armed-high-energy-lasers-may-arrive-2017/121583/
http://www.gizmag.com/lockheed-martin-tests-laser-turret-warplanes/39898/