High-order Bessel beams are of great interest for most stable long-range optical quantum communications due to their unique nondiffraction,self-healing,and orbital angular-momentum-carrying capabilities.Until now,meta...High-order Bessel beams are of great interest for most stable long-range optical quantum communications due to their unique nondiffraction,self-healing,and orbital angular-momentum-carrying capabilities.Until now,metasurfaces based on Bessel beam generators are mostly static and focused on generating zero-order Bessel beams.A moirémeta-device made of two cascaded metasurfaces is a simple,effective strategy to dynamically manipulate the wavefront of electromagnetic(EM)waves by mutual rotation between the two metasurfaces.Here,an all-dielectric moirémeta-device integrated with the functions of an axicon and a spiral phase plate to generate terahertz Bessel beams is designed.Not only the order,but also the nondiffraction length of the generated Bessel beam can be continuously tuned.As a proof of concept of the feasibility of the platform,the case of tuning order is experimentally demonstrated.The experimental results are in good agreement with the theoretical expectations.In addition,we also numerically proved that the nondiffraction length of the Bessel beam can be adjusted with the same approach.The moirémeta-device platform is powerful in dynamically manipulating the wavefront of EM waves and provides an effective strategy for continuously controlling the properties of the Bessel beam,which may find applications in optical communications,particle manipulation,and super-resolution imaging.展开更多
Graphene-based terahertz(THz)metasurfaces combined with metallic antennas have the advantages of ultrasmall thickness,electrical tunability,and fast tuning speed.However,their tuning ability is limited by nonindepende...Graphene-based terahertz(THz)metasurfaces combined with metallic antennas have the advantages of ultrasmall thickness,electrical tunability,and fast tuning speed.However,their tuning ability is limited by nonindependently tunable pixels and low modulation depth due to the ultra-small thickness of graphene.Here,we demonstrate a reconfigurable THz phase modulator with 5×5 independently tunable units enabled by switching the voltages applied on 10 graphene ribbons prepared by laser cutting.In addition,by introducing quasibound states in the continuum resonance through a designed double C-shaped antenna,the efficiency of the device is enhanced by 2.7–3.6 times under different graphene chemical potentials.Experimental results demonstrate that a focus can be formed,and the focal length is changed from 14.3 mm to 22.6 mm.This work provides potential for compact THz spatial light modulators that may be applied in THz communication,detection,and imaging.展开更多
基金Capacity Building for Science and Technology Innovation-Fundamental Scientific Research Funds(00820531120017)Sino-German Mobility Program of the Sino-German Center for Science Funding(M-0225)+2 种基金Beijing Talents Project(2018A19)National Key Research and Development Program of China(2019YFC1711905)National Natural Science Foundation of China(61875010,11874132,1174243,11774246)。
文摘High-order Bessel beams are of great interest for most stable long-range optical quantum communications due to their unique nondiffraction,self-healing,and orbital angular-momentum-carrying capabilities.Until now,metasurfaces based on Bessel beam generators are mostly static and focused on generating zero-order Bessel beams.A moirémeta-device made of two cascaded metasurfaces is a simple,effective strategy to dynamically manipulate the wavefront of electromagnetic(EM)waves by mutual rotation between the two metasurfaces.Here,an all-dielectric moirémeta-device integrated with the functions of an axicon and a spiral phase plate to generate terahertz Bessel beams is designed.Not only the order,but also the nondiffraction length of the generated Bessel beam can be continuously tuned.As a proof of concept of the feasibility of the platform,the case of tuning order is experimentally demonstrated.The experimental results are in good agreement with the theoretical expectations.In addition,we also numerically proved that the nondiffraction length of the Bessel beam can be adjusted with the same approach.The moirémeta-device platform is powerful in dynamically manipulating the wavefront of EM waves and provides an effective strategy for continuously controlling the properties of the Bessel beam,which may find applications in optical communications,particle manipulation,and super-resolution imaging.
基金Beijing Municipal Natural Science Foundation (L223031)National Natural Science Foundation of China (61875010)。
文摘Graphene-based terahertz(THz)metasurfaces combined with metallic antennas have the advantages of ultrasmall thickness,electrical tunability,and fast tuning speed.However,their tuning ability is limited by nonindependently tunable pixels and low modulation depth due to the ultra-small thickness of graphene.Here,we demonstrate a reconfigurable THz phase modulator with 5×5 independently tunable units enabled by switching the voltages applied on 10 graphene ribbons prepared by laser cutting.In addition,by introducing quasibound states in the continuum resonance through a designed double C-shaped antenna,the efficiency of the device is enhanced by 2.7–3.6 times under different graphene chemical potentials.Experimental results demonstrate that a focus can be formed,and the focal length is changed from 14.3 mm to 22.6 mm.This work provides potential for compact THz spatial light modulators that may be applied in THz communication,detection,and imaging.
