EXPERIMENTAL EVALUATION OF A 2-PHOTON WAVE-PACKET IN TYPE-II PARAMETRIC DOWNCONVERSION

A two-photon wave packet (a biphoton) produced by type-If parametric d ownconversion is studied in a simple beam-splitting experiment for its natural shape in space-time. The measured triangular shape of a two-p hoton correlation function is the signature of a rectangular-shaped bi photon. Inserting a birefringent sample into the beam causes a displac ement of the vertex of the notch pattern, which can be used to measure the optical delay between the ordinary and the extraordinary rays in the sample with femtosecond resolution.