Space-time coupling in upconversion of broadband downconverted light

We investigate the upconversion process of broadband incoherent light generated by parametric downconversion. We focus on the incoherent component of the sum-frequency generated (SFG) radiation, analyzing its spatiotemporal properties. We show that its spectrum has a skewed geometry in space-time, originating from a compensation between the group-velocity mismatch and the spatial walk-off of the fundamental and the SFG fields. The results are illustrated by a theoretical modeling of the optical system and by experimental measurements. (C) 2014 Optical Society of America