Coherence properties of high-gain twin beams generated in pump-depletion   regime
  Twin-beam coherence properties are analyzed both in the spatial and spectral domains at high-gain regime including pump depletion. The increase of the size of intensity auto- and cross-correlation areas at increasing pump power is replaced by a decrease in the pump depletion regime. This effect is interpreted as a progressive loss in the mode selection occurring at high-gain amplification. The experimental determination of the number of spatio-spectral modes from $g^{(2)} $-function measurements confirms this explanation. 
Alessia Allevi, Ottavia Jedrkiewicz, Enrico Brambilla, Alessandra   Gatti, Jan Perina Jr., O. Haderka, and Maria Bondani
quant-ph physics.optics