| Chirality exists in every aspect of our daily life.The research on the mechanism of chirality has a profound impact on many fields of nature sciences.The chiral optical response of artificial micro-/nano-structures is crucial for the design of optical devices,selective separation of enantiomers,biosensing applications and so on.Recently,more and more attentions have been paid to the technique of nano-kirigami to prepare metasurface for controlling light-matter interaction.In this paper,the chiral optical response of meta-molecular arrays with various morphologies is studied based on the fabrication method of nano-kirigami,benefited from which the large scale engineering of circular dichroism(CD)under deformation perturbation is realized and the sensing applications are explored.The main contents are as follows:(1)A series of chiral meta-molecules with triple rotational symmetry arranged in hexagonal lattice arrays are designed by using the method of nano-kirigami,and some kinds of novel deformable three-dimensional metasurfaces are proposed.By means of tuning the etching pattern of the two-dimensional(2D)precursor and focused ion beam(FIB)irradiation region,a variety of three-dimensional(3D)meta-molecular morphologies are designed and flexible regulation of chiral light-matter interactions is realized.Normalized surface electric field distribution and multipole moment scattering power are plotted for theoretical analysis of chiral responses.(2)The closed-loop nano-kirigami structures are first designed.As the etching length of the slits in the two-dimensional pattern are fine-tuned,the excitation of the surface lattice resonance(SLR)of the chiral meta-molecules can be sensitively regulated,and the chiral optical response can be reversed.The chirality of the SLR is switched by strong coupling between meta-molecules when the slit length is only reduced by 190 nm.The CD peak with amplitude of+0.44 at the SLR wavelength is transformed into a CD dip with amplitude of-0.66.Moreover,boolean irradiation in different regions on the same 2D array results in the changes of deformation region of the mata-moleculars and causes the sign reversal of CD in the near-infrared region.(3)The open-loop structure with weak SLR can be obtained by removing the central disk in the closed-loop structure.The open-loop structure has the advantages of small footprint,flexible control and simple preparation.Transferring the sharp angle of the meta-molecular from the top of the structure to the bottom greatly enhances the chiral surface lattice resonance,resulting in enhanced CD.Moreover,through the swing of the arms,the amplitude of CD is drastically reversed near the lattice period,with a positive value of+0.40 evolving into a negative value of-0.54.(4)It is found in this study that the refractive index of asymmetric environmental media will greatly attenuate the lattice resonance of chiral surface.By simulating CD spectra under different environmental refractive indices,it is obtained that the wavelength of CD peaks varies linearly with the refractive index of the top surface within a certain range,which can flexibly regulate the wavelength,intensity and symbol of CD.Based on the performance of CD spectra under different ambient refractive indices,we designed a refractive index sensor modulated by wavelength with a sensitivity of 1133 nm RIU-1,which provides an ideal platform for the measurement and application of refractive index sensing. |
PDF Full Text Request