The recently proposed extreme-ultraviolet beams with time-varying orbital angular momentum(OAM)realized by high-harmonic generation provide extraordinary tools for quantum excitation control and particle manipulation....The recently proposed extreme-ultraviolet beams with time-varying orbital angular momentum(OAM)realized by high-harmonic generation provide extraordinary tools for quantum excitation control and particle manipulation.However,such an approach is not easily scalable to other frequency regimes.We design a space-time-coding digital metasurface operating in the microwave regime to experimentally generate time-varying OAM beams.Due to the flexible programmability of the metasurface,a higher-order twist in the envelope wavefront structure of time-varying OAM beams can be further designed as an additional degree of freedom.The time-varying OAM field patterns are dynamically mapped by developing a two-probe measurement technique.Our approach in combining the programmability of space-time-coding digital metasurfaces and the two-probe measurement technique provides a versatile platform for generating and observing time-varying OAM and other spatiotemporal excitations in general.The proposed time-varying OAM beams have application potentials in particle manipulation,time-division multiplexing,and information encryption.展开更多
基金This work was supported by the Hong Kong Research Grants Council(Project Nos.R6015-18 and C6012-20G).
文摘The recently proposed extreme-ultraviolet beams with time-varying orbital angular momentum(OAM)realized by high-harmonic generation provide extraordinary tools for quantum excitation control and particle manipulation.However,such an approach is not easily scalable to other frequency regimes.We design a space-time-coding digital metasurface operating in the microwave regime to experimentally generate time-varying OAM beams.Due to the flexible programmability of the metasurface,a higher-order twist in the envelope wavefront structure of time-varying OAM beams can be further designed as an additional degree of freedom.The time-varying OAM field patterns are dynamically mapped by developing a two-probe measurement technique.Our approach in combining the programmability of space-time-coding digital metasurfaces and the two-probe measurement technique provides a versatile platform for generating and observing time-varying OAM and other spatiotemporal excitations in general.The proposed time-varying OAM beams have application potentials in particle manipulation,time-division multiplexing,and information encryption.
