On Divergence in Radiation Fields
  Three thought experiments demonstrate that under certain circumstances electromagnetic fields have to be attenuated or amplified multiplicatively in order not to violate the conservation of energy. Modulation of radiation by means other than superposition is theoretically made possible by plugging additional terms into the source slots of the Maxwell equations. Thus modulated radiation would enable the well focused stimulation of neurons for diagnostic and therapeutic purposes and for HCI applications. 
Joerg Fricke
physics.class-ph