Two-Dimensional Spatial Solitary Waves from Traveling-Wave Parametric Amplification of the Quantum Noise

In a single 15-mm lithium triborate crystal, operated at high gain and strong diffraction, we obtained the spatial mode locking of the quantum noise, its amplification up to the pump level, and quasisoliton propagation of the mutually trapped beams. Visible pulses of 1 $\mu \mathrm{J}$ 1.5 ps were converted, with $50\%$ efficiency, into diffraction-limited superfluorescence, tunable in the range 0.67– $2.5\mu \mathrm{m}$.