Metamaterials composed of metallic antennae arrays are used as they possess extraordinary optical transmission(EOT)in the terahertz(THz)region,whereby a giant forward light propagation can be created using constructiv...Metamaterials composed of metallic antennae arrays are used as they possess extraordinary optical transmission(EOT)in the terahertz(THz)region,whereby a giant forward light propagation can be created using constructive interference of tunneling surface plasmonic waves.However,numerous applications of THz meta-devices demand an active manipula-tion of the THz beam in free space.Although some studies have been carried out to control the EOT for the THz region,few of these are based upon electrical modulation of the EOT phenomenon,and novel strategies are required for act-ively and dynamically reconfigurable EOT meta-devices.In this work,we experimentally present that the EOT resonance can be coupled to optically reconfigurable chalcogenide metamaterials which offers a reversible all-optical control of the THz light.A modulation efficiency of 88%in transmission at 0.85 THz is experimentally observed using the EOT metama-terials,which is composed of a gold(Au)circular aperture array sitting on a non-volatile chalcogenide phase change ma-terial(Ge2Sb2Te5)film.This comes up with a robust and ultrafast reconfigurable EOT over 20 times of switching,excited by a nanosecond pulsed laser.The measured data have a good agreement with finite-element-method numerical simula-tion.This work promises THz modulators with significant on/off ratios and fast speeds.展开更多
High-performance terahertz(THz)devices with reconfigurable features are highly desirable in many promising THz applications.However,most of the existing reconfigurable THz elements are still limited to volatile respon...High-performance terahertz(THz)devices with reconfigurable features are highly desirable in many promising THz applications.However,most of the existing reconfigurable THz elements are still limited to volatile responses,single functionality,and time-consuming multistep manufacturing procedures.In this paper,we report a lithography-free approach to create reconfigurable and nonvolatile THz components by exploring the reversible,nonvolatile,and continuous THz modulation capability of the phase change material Ge_(2)Sb_(2)Te_(5).As a proof of concept,THz gratings with significant Rayleigh anomalies and diffraction as well as ultrathin THz flat lenses with subwavelength and ultra-broadband focusing capabilities are designed and fabricated on ultrathin Ge_(2)Sb_(2)Te_(5)films using the presented photo-imprint strategy.Moreover,such a method can also be adopted to create more complex THz devices,such as Pancharatnam–Berry phase metasurfaces and grayscale holographic plates.With these findings,the proposed method will provide a promising solution to realize reconfigurable and nonvolatile THz elements.展开更多
Metasurfaces,especially tunable ones,have played a major role in controlling the amplitude,phase,and polarization of electromagnetic waves and attracted growing interest,with a view toward a new generation of miniatur...Metasurfaces,especially tunable ones,have played a major role in controlling the amplitude,phase,and polarization of electromagnetic waves and attracted growing interest,with a view toward a new generation of miniaturized devices.However,to date,most existing reconfigurable devices are bounded in volatile nature with sustained external energy to maintain and single functionality,which restrict their further applications.Here,we demonstrate for the first time,to our knowledge,nonvolatile,reconfigurable,and dynamic Janus metasurfaces by incorporating phase-change material Ge_(2)Se_(2)Te_(5)(GST)in the terahertz(THz)regime.First,we experimentally show the reversible switching characteristic of GST on large areas by applying a single nanosecond laser pulse,which exhibits excellent contrast of THz properties in both states.Then,we present a multiplex metasurface scheme.In each metasurface,three sets of structures are adopted,in which two sets integrate GST.The effective structures can be reversely modulated by the amorphization and crystallization of GST.As a proof of concept,the dynamic beam splitter,bifocal metalens,dual-mode focusing optical vortex generators,and switchable metalens/focusing optical vortex generators are designed,fabricated,and experimentally characterized,and can be switched reversibly and repeatedly with the help of optical and thermal stimuli.Our scheme will pave the way toward the development of multifunctional and compact THz devices and may find use for applications in THz imaging,sensing,and communications.展开更多
Actively controlling the polarization states of terahertz(THz)waves is essential for polarization-sensitive spectroscopy,which has various applications in anisotropy imaging,noncontact Hall measurement,and vibrational...Actively controlling the polarization states of terahertz(THz)waves is essential for polarization-sensitive spectroscopy,which has various applications in anisotropy imaging,noncontact Hall measurement,and vibrational circular dichroism.In the THz regime,the lack of a polarization modulator hinders the development of this spectroscopy.We theoretically and experimentally demonstrate that conjugated bilayer chiral metamaterials(CMMs)integrated with Ge_(2)Sb_(2)Te_(5)(GST225)active components can achieve nonvolatile and continuously tunable optical activity in the THz region.A THz time-domain spectroscopic system was used to characterize the device,showing a tunable ellipticity(from‒36°to 0°)and rotation of the plane polarization(from 32°to 0°)at approximately 0.73 THz by varying the GST225 state from amorphous(AM)to crystalline(CR).Moreover,a continuously tunable chiroptical response was experimentally observed by partially crystallizing the GST225,which can create intermediate states,having regions of both AM and CR states.Note that the GST225 has an advantage of nonvolatility over the other active elements and does not require any energy to retain its structural state.Our work allows the development of THz metadevices capable of actively manipulating the polarization of THz waves and may find applications for dynamically tunable THz circular polarizers and polarization modulators for THz emissions.展开更多
文摘Metamaterials composed of metallic antennae arrays are used as they possess extraordinary optical transmission(EOT)in the terahertz(THz)region,whereby a giant forward light propagation can be created using constructive interference of tunneling surface plasmonic waves.However,numerous applications of THz meta-devices demand an active manipula-tion of the THz beam in free space.Although some studies have been carried out to control the EOT for the THz region,few of these are based upon electrical modulation of the EOT phenomenon,and novel strategies are required for act-ively and dynamically reconfigurable EOT meta-devices.In this work,we experimentally present that the EOT resonance can be coupled to optically reconfigurable chalcogenide metamaterials which offers a reversible all-optical control of the THz light.A modulation efficiency of 88%in transmission at 0.85 THz is experimentally observed using the EOT metama-terials,which is composed of a gold(Au)circular aperture array sitting on a non-volatile chalcogenide phase change ma-terial(Ge2Sb2Te5)film.This comes up with a robust and ultrafast reconfigurable EOT over 20 times of switching,excited by a nanosecond pulsed laser.The measured data have a good agreement with finite-element-method numerical simula-tion.This work promises THz modulators with significant on/off ratios and fast speeds.
基金Key Fund of Shenzhen Natural Science Foundation(JCYJ20200109150212515)Tianjin Municipal Fund for Distinguished Young Scholars(20JCJQJC00190)+1 种基金National Natural Science Foundation of China(62235013)National Key Research and Development Program of China(2017YFA0701004,2019YFA0709100,2020YFA0714504)。
文摘High-performance terahertz(THz)devices with reconfigurable features are highly desirable in many promising THz applications.However,most of the existing reconfigurable THz elements are still limited to volatile responses,single functionality,and time-consuming multistep manufacturing procedures.In this paper,we report a lithography-free approach to create reconfigurable and nonvolatile THz components by exploring the reversible,nonvolatile,and continuous THz modulation capability of the phase change material Ge_(2)Sb_(2)Te_(5).As a proof of concept,THz gratings with significant Rayleigh anomalies and diffraction as well as ultrathin THz flat lenses with subwavelength and ultra-broadband focusing capabilities are designed and fabricated on ultrathin Ge_(2)Sb_(2)Te_(5)films using the presented photo-imprint strategy.Moreover,such a method can also be adopted to create more complex THz devices,such as Pancharatnam–Berry phase metasurfaces and grayscale holographic plates.With these findings,the proposed method will provide a promising solution to realize reconfigurable and nonvolatile THz elements.
基金National Key Research and Development Program of China(2017YFA0701004,2019YFA0709100,2020YFA0714504)Tianjin Municipal Fund for Distinguished Young Scholars(20JCJQJC00190)Key Fund of Shenzhen Natural Science Foundation(JCYJ20200109150212515)。
文摘Metasurfaces,especially tunable ones,have played a major role in controlling the amplitude,phase,and polarization of electromagnetic waves and attracted growing interest,with a view toward a new generation of miniaturized devices.However,to date,most existing reconfigurable devices are bounded in volatile nature with sustained external energy to maintain and single functionality,which restrict their further applications.Here,we demonstrate for the first time,to our knowledge,nonvolatile,reconfigurable,and dynamic Janus metasurfaces by incorporating phase-change material Ge_(2)Se_(2)Te_(5)(GST)in the terahertz(THz)regime.First,we experimentally show the reversible switching characteristic of GST on large areas by applying a single nanosecond laser pulse,which exhibits excellent contrast of THz properties in both states.Then,we present a multiplex metasurface scheme.In each metasurface,three sets of structures are adopted,in which two sets integrate GST.The effective structures can be reversely modulated by the amorphization and crystallization of GST.As a proof of concept,the dynamic beam splitter,bifocal metalens,dual-mode focusing optical vortex generators,and switchable metalens/focusing optical vortex generators are designed,fabricated,and experimentally characterized,and can be switched reversibly and repeatedly with the help of optical and thermal stimuli.Our scheme will pave the way toward the development of multifunctional and compact THz devices and may find use for applications in THz imaging,sensing,and communications.
基金the National Key Research and Development Program of China(2019YFA0709100,2020YFA0714504)the LiaoNing Revitalization Talents Program(Grant No.XLYC1807237).
文摘Actively controlling the polarization states of terahertz(THz)waves is essential for polarization-sensitive spectroscopy,which has various applications in anisotropy imaging,noncontact Hall measurement,and vibrational circular dichroism.In the THz regime,the lack of a polarization modulator hinders the development of this spectroscopy.We theoretically and experimentally demonstrate that conjugated bilayer chiral metamaterials(CMMs)integrated with Ge_(2)Sb_(2)Te_(5)(GST225)active components can achieve nonvolatile and continuously tunable optical activity in the THz region.A THz time-domain spectroscopic system was used to characterize the device,showing a tunable ellipticity(from‒36°to 0°)and rotation of the plane polarization(from 32°to 0°)at approximately 0.73 THz by varying the GST225 state from amorphous(AM)to crystalline(CR).Moreover,a continuously tunable chiroptical response was experimentally observed by partially crystallizing the GST225,which can create intermediate states,having regions of both AM and CR states.Note that the GST225 has an advantage of nonvolatility over the other active elements and does not require any energy to retain its structural state.Our work allows the development of THz metadevices capable of actively manipulating the polarization of THz waves and may find applications for dynamically tunable THz circular polarizers and polarization modulators for THz emissions.