GENERATION OF SUB-POISSONIAN LIGHT USING ACTIVE CONTROL WITH TWIN BEAMS

We present a general theory for intensity noise reduction when one beam of light is used to control another. We use a semiclassical input-output formalism and determine the conditions necessary for noise reduction below the shot-noise level. Configurations are examined where the intensity of one beam is monitored and control is effected directly to the other beam (feedforward), or indirectly through the beam source (feedback). The results are applied to the case of twin beams generated by an optical parametric oscillator. We detail for this system the implementation of an electro-optic control channel. Finally, a comparison is made between theory and experiment.