Chiral molecules that do not superimpose on their mirror images are the foundation of all life forms on earth.Chiral molecules exhibit chiroptical responses,i.e.,they have different electromagnetic responses to light ...Chiral molecules that do not superimpose on their mirror images are the foundation of all life forms on earth.Chiral molecules exhibit chiroptical responses,i.e.,they have different electromagnetic responses to light of different circular polarizations.However,chiroptical responses in natural materials,such as circular dichroism and optical rotation dispersion,are intrinsically small because the size of a chiral molecule is significantly shorter than the wavelength of electromagnetic wave.Conventional technology for enhancing chiroptical signal entails demanding requirements on precise alignment of the chiral molecules to certain nanostructures,which however only leads to a limited performance.Herein,we show a new approach towards enhancement of chiroptical effects through a Fabry-Pérot(FP)cavity formed by two handedness-preserving metamirrors operating in the GHz region.We experimentally show that the FP cavity resonator can enhance the optical activity of the chiral molecule by an order of magnitude.Our approach may pave the way towards state-of-the-art chiral sensing applications.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
基金This work was supported by the International Science and Technology Cooperation Programme of China(grant no.2015DFG12630)T.C.acknowledges support from the Program for Liaoning Excellent Talents in University(grant no.LJQ2015021).
文摘Chiral molecules that do not superimpose on their mirror images are the foundation of all life forms on earth.Chiral molecules exhibit chiroptical responses,i.e.,they have different electromagnetic responses to light of different circular polarizations.However,chiroptical responses in natural materials,such as circular dichroism and optical rotation dispersion,are intrinsically small because the size of a chiral molecule is significantly shorter than the wavelength of electromagnetic wave.Conventional technology for enhancing chiroptical signal entails demanding requirements on precise alignment of the chiral molecules to certain nanostructures,which however only leads to a limited performance.Herein,we show a new approach towards enhancement of chiroptical effects through a Fabry-Pérot(FP)cavity formed by two handedness-preserving metamirrors operating in the GHz region.We experimentally show that the FP cavity resonator can enhance the optical activity of the chiral molecule by an order of magnitude.Our approach may pave the way towards state-of-the-art chiral sensing applications.
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.
