We report what is, to the best of our knowledge, the first experiment on third-order optical difference frequency generation. The nonlinear medium is a phase-matched KTiOPO<sub>4</sub> crystal pumped at 532 and 1665 nm in the picosecond regime. The proposed experimental configuration leads to an efficient and pure cubic process, with generation of 4.5μJ/pulse at 1474 nm. This result opens the way to new quantum experiments on three-photon Greenberger–Horne–Zeilinger entanglement.
© 2004 Optical Society of America
J. Douady and B. Boulanger, "Experimental demonstration of a pure third-order optical parametric downconversion process," Opt. Lett. 29, 2794-2796 (2004)