Itisshownthatorbitalangularmomentum(OAM)isapromisingnewresourceinfutureclassicalandquantumcommunications.However,theseparationofOAMmodesisstillabigchallenge.Inthispaper,weproposeasimpleandefficientseparationmethodwitharadialvaryingphase.Inthemethod,specificradialvaryingphasesaredesignedandmodulatedfordifferentOAMmodes.Theresultantbeamisfocusedtothespotswithdifferenthorizontalandverticalpositionsafteraconvexlens,whenthecoordinatetransformation,includingtwoopticalelementswithcoordinatetransformationphaseandcorrectphase,operatesonthereceivedbeam.Thehorizontalpositionofthespotisdeterminedbythevortexphases,andtheverticalpositionofthespotisdependentontheradialvaryingphases.ThesimulationandexperimentalresultsshowthattheproposedmethodisfeasiblebothforseparationoftwoOAMmodesandseparationofthreeOAMmodes.TheproposedseparationmethodisavailableinprincipleforanyneighboringOAMmodesbecausetheradialvaryingphaseiscontrolled.Additionally,noextrainstrumentsareintroduced,andthereisnodiffractionandnarrowingprocesslimitationfortheseparation.
