Spatio-spectral characterization of twin-beam states of light for quantum state engineering

We present an experimental investigation of the spatio-spectral coherence properties of bright twin-beam states (TWBs) as functions of different parameters, such as pump mean power and tuning angle of the employed nonlinear crystal. Our attention is mainly focused on the possible relations among the different quantities under investigation. Particular attention is devoted to the evolution of the number of spatio-spectral modes describing the radiation fi ̄eld, as it represents an interesting property to be controlled in view of possible applications to quantum state engineering protocols.