X -shaped space-time coherence in optical parametric generation
Résumé
We study the spatiotemporal coherence properties of superfluorescence radiation generated in optical para-
metric amplification of quantum noise. We show that the angular dispersion properties of the spatiotemporal
spectra, measured in different phase-matching conditions, lead to a clear X-shaped structure of the mutual
correlation function of the radiation. Within a statistical picture, we interpret the generated superfluorescence as
a stochastic “gas” of quasistationary modes characterized by a skewed correlation in the spatiotemporal do-
main, with characteristics similar to linear and nonlinear X waves not describable within a separable approach
in space and time.