The Investigation Of Enhanced Circular Dichroism With Surface Lattice Mode In Noble Metallic Nanoparticle Arrays

The localized surface plasmon resonance of the noble metallic nanostructure can effectively increase the interaction with the external light field,so it has a rich application prospect in the field of micro-nano photonics.Relative to the chiral molecules,for example,circular dichroism intensity of chiral metallic nanostructure can get improvement of several orders of magnitude,and response spectrum can be extended to the visible to near infrared wave band.It can be used to design ultrathin wave plate,high sensitivity sensor,such as nano photonic devices.Including how to improve the strength of circular dichroism response is the key to realize these applications.Due to the existence of radiation loss,it is not conducive to improve chiral response of noble metallic nanostructure because of the low quality factor.When the nanoparticles form a periodic array structure,they are tuned by adjusting the period of array and the localized surface plasmon resonance.The coupling between localized surface plasmon resonances and Rayleigh anomalies can be realized.Therefore,the surface lattice resonance with large Q-factors can effectively suppress radiative losses and enhance the interaction with the external light field.Based on the above properties of the surface lattice resonance,this paper put forward of chiral metallic nanostructure arrays,through the adjustment period of array to achieve surface lattice resonance excitation,so as to improve its strength of circular dichroism responses.The paper was designed and studied the two types of chiral array structure,namely the split resonances ring dimers arrays and nano dish of the quadrumer array.The numerical calculation results show that when introducing the surface lattice resonance,indeed can effectively enhance the strength of circular dichroism responses:(1)In the chiral split ring resonances dimers arrays,adopts the left-hand circularly polarized light or right-handed circularly polarized light,which can selectively excitation surface lattice mode of formation by the localized surface plasmonic from the primary resonance and Rayleigh abnormalies diffraction coupling.Compared with the structure without diffraction coupling,this model increase the absorption difference of two circularly polarized light,and then enhance the intrinsic circular dichromatic response of the array.In the case of localized resonance,the transmittance difference is only 0.12.When the surface lattice resonance exists,the transmittance difference can be increased to about 0.7.(2)In the chiral arrays of nano disk quadrumer,the surface lattice resonance can also be used to enhance the circular dichroism.And research shows that localized surface plasmon resonance and Rayleigh abnormalies diffraction coupling form the surface lattice mode.It not need the refractive index matching conditions and control the mulch or basal refractive index to adjust its circular dichroism response.Therefore,it is expected to realize the dynamic regulation of circular dichromatism without changing the nanostructure.In addition,in order to better understand the surface lattice resonance enhanced circular dichromatic mechanism,we adopted the improved Born-Kuhn model to analyze the chiral response characteristics.