Artificial structures provide an efficient method to generate acoustic vortices carrying orbital angular momentum(OAM)essential for applications ranging from object manipulation to acoustic communica-tion.However,their flexibility in terms of chirality control has thus far been limited by the lack of recon-figurability and degrees of freedom like spin-orbit coupling.Here we show that this restriction can be lifted by controlling the individual on-off states of two coherent monopolar sources inside a passive parity-time-symmetric ring cavity at an exceptional point where the counter-propagating waves coalesce into one chiral eigenmode.One of the sources satisfies the chirality-reversal condition,generating a trav-elling wave field fully decoupled from and opposite to the chiral eigenmode,while the other source is phase-shifted such that the wave generated by the first source can be canceled out,and the remaining sound field circulates in the same direction as the chiral eigenmode.Such non-Hermitian selective exci-tation enables our experimental realization of acoustic vortex emission with switchable OAM but free of system reconfiguration.Our work offers opportunities for chiral sound manipulation as well as integrated and tunable acoustic OAM devices.

Tuo Liu;Shuowei An;Zhongming Gu;Shanjun Liang;He Gao;Guancong Ma;Jie Zhu

Key Laboratory of Noise and Vibration Research,Institute of Acoustics,Chinese Academy of Sciences,Beijing 100190,China;Department of Mechanical Engineering,The Hong Kong Polytechnic University,Hong Kong,China;The Hong Kong Polytechnic University Shenzhen Research Institute,Shenzhen 518057,China;Institute of Acoustics,School of Physics Science and Engineering,Tongji University,Shanghai 200092,China;Division of Science,Engineering and Health Studies,College of Professional and Continuing Education,The Hong Kong Polytechnic University,Hong Kong,China;Department of Physics,Hong Kong Baptist University,Hong Kong,China

科学通报（英文版）

[1]Tuo Liu;Shuowei An;Zhongming Gu;Shanjun Liang;He Gao;Guancong Ma;Jie Zhu-.Chirality-switchable acoustic vortex emission via non-Hermitian selective excitation at an exceptional point)[J].科学通报（英文版）,2022(11):1131-1136

figurability,monopolar

Chirality,switchable,acoustic,vortex,emission,via,Hermitian,selective,excitation,exceptional,point,Artificial,structures,provide,efficient,method,vortices,carrying,orbital,angular,momentum,OAM,essential,applications,ranging,from,object,manipulation,communica,However,their,flexibility,terms,chirality,thus,far,been,limited,by,lack,degrees,freedom,like,spin,coupling,Here,show,that,this,restriction,lifted,controlling,individual,states,two,coherent,sources,inside,passive,parity,symmetric,ring,cavity,where,counter,propagating,waves,coalesce,into,one,eigenmode,One,satisfies,reversal,condition,generating,trav,elling,field,fully,decoupled,opposite,while,other,phase,shifted,such,generated,first,canceled,out,remaining,sound,circulates,same,direction,Such,enables,experimental,realization,but,system,reconfiguration,Our,work,offers,opportunities,well,integrated,tunable,devices

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