  We report on a novel electro-optic device for the diagnostics of high
repetition rate laser systems. It is composed of a microwave receiver and of a
second order nonlinear crystal, whose irradiation with a train of short laser
pulses produces a time-dependent polarization in the crystal itself as a
consequence of optical rectification. This process gives rise to the emission
of microwave radiation that is detected by a receiver and is analyzed to infer
the repetition rate and intensity of the pulses.
  We believe that this new method may overcome some of the limitations of
photodetection techniques.
