Duetotheexistenceofspatialwalk-offand/orgroup-velocitymismatcheffects,pump-to-signalphasetransferbecomesinevitableduringparametricamplification.Weexperimentallydemonstratethatinhybridseededopticalparametricamplifiers(OPAs)thatincludetwoOPAstagesseededbythesignalandidlerwaves,respectively,thephaseoftheoutputsignalcanberestoredtoitsinitialvalue,althoughtherearespatialandtemporalphasefluctuationsonthepumpsource.Thismethodsignificantlyrelaxestherequirementforhighpumpbeamquality,whichisalwaysverystringentinparametricamplificationsystems.Withtheintroductionofthisschemeintobirefringentphase-matchingOPAsorchirped-pulseOPAs,itshouldbepromisingtoachieveintensefemtosecondlaserpulsesthatareclosetothediffractionlimitinspaceandultra-highcontrastintime,simultaneously.
