title: Observation of triply coincident nonlinearities in periodically poled KTiOPO4.
abstract: We report the simultaneous quasi-phase-matching of all three possible nonlinearities for propagation along the X axis of periodically poled (PP) KTiOPO4 (KTP) for second-harmonic generation of 745 nm pulsed light from 1490 nm subpicosecond pulses in a PPKTP crystal with a 45.65 microm poling period. This confirms the recent Sellmeier fits for KTP by Kato and Takaoka [Appl. Opt. 41, 5040 (2002)]. Such coincident nonlinearities are of importance for realizing compact sources of multipartite continuous-variable entanglement [Pfister et al., Phys. Rev. A 70, 020302 (2004)], and we propose a new simpler method for entangling four fields on the basis of this triple coincidence.
authors.affiliation: Department of Physics, University of Virginia, 382 McCormick Road, Charlottesville, Virginia 22904-4714, USA.
authors.forename: Raphael C
authors.initials: RC
authors.lastname: Pooser
authors.forename: Olivier
authors.initials: O
authors.lastname: Pfister