Spatial coherence effects on second- and fourth-order temporal interference.
We report the results of two experiments performed with two-photon light, produced via collinear degenerate optical spontaneous parametric downconversion (SPDC), in which both second-order (one-photon) and fourth-order (two-photon) interferograms are recorded in a Mach-Zehnder interferometer (MZI). In the first experiment, high-visibility fringes are obtained for both the second- and fourth-order interferograms. In the second experiment, the MZI is modified by the removal of a mirror from one of its arms; this leaves the fourth-order interferogram unchanged, but extinguishes the second-order interferogram. A theoretical model that takes into consideration both the temporal and spatial degrees-of-freedom of the two-photon state successfully explains the results. While the temporal interference in the MZI is independent of the spatial coherence of the source, that of the modified MZI is not.
Lincoln Laboratory, Massachusetts Institute of Technology, 244 Wood Street, Lexington, Massachusetts 02420-9108, USA.
Timothy
T
Yarnall
Ayman F
AF
Abouraddy
Bahaa E A
BE
Saleh
Malvin C
MC
Teich
D003198:Computer Simulation; D007368:Interferometry / Q000379:methods*; D008027:Light; D008962:Models, Theoretical; D017785:Photons; D012031:Refractometry / Q000379:methods*; D012542:Scattering, Radiation; D041623:Tomography, Optical Coherence / Q000379:methods*