  We investigate the quantum state generated by optical parametric
down-conversion in a $\chi^{(2) } $ medium driven by two noncollinear light
modes. The analysis shows the emergence of multipartite, namely 3- or
4-partite, entangled states in a subset of the spatio-temporal modes generated
by the process. These appear as bright spots against the background
fluorescence, providing an interesting analogy with the phenomenology recently
observed in two-dimensional nonlinear photonic crystals. We study two realistic
setups: i) Non-critical phase-matching in a periodically poled Lithium
Tantalate slab, characterized by a 3-mode entangled state among hot spots. ii)
A type I setup in a Beta-Barium Borate crystal, where the spatial walk-off
between the two pumps can be exploited to make a transition to a quadripartite
entangled state. In both cases we show that the properties of the state can be
controlled by modulating the relative intensity of two pump waves, making the
device a versatile tool for quantum state engineering.
