  We report on the observation of an unusual type of parametric
down-conversion. In the regime where collinear degenerate emission is in the
anomalous range of group-velocity dispersion, its spectrum is restricted in
both angle and wavelength. Detuning from exact collinear-degenerate
phasematching leads to a ring shape of the wavelength-angular spectrum,
suggesting a new type of spatiotemporal coherence and entanglement of photon
pairs. By imposing a phase varying in a specific way in both angle and
wavelength, one can obtain an interesting state of an entangled photon pair,
with the two photons being never at the same point at the same time.
