We report two-photon correlation experiments using spontaneous parametric down-conversion under a severe manipulation of the input pump field. Considering the case of passing the laser beam through a focusing lens before the down-conversion crystal, theoretical calculations and a series of imaging experiments demonstrate two-photon geometric optics effects. In particular, the imaging in coincidence counts of an aperture placed in one of the down-conversion beams is found to be the analog of a simple spherical mirror system, which displays a ‘‘vacuum dispersion’’ effect in that the object and image distances are wavelength weighted. © 1996 The American Physical Society.

• Received 10 October 1995

DOI:https://doi.org/10.1103/PhysRevA.53.2804