Sps' Properties Of Subwavelength Symmetry Broken Unit Structural Hole Arrays

The enhanced optical transmission characteristics of metal micro-nanostructures is a research hotspot in the field of Plasmonics,which has important applications in nanophotonic devices,molecular detection,and biosciences.The finite-difference time-domain(FDTD)method is employed to explore the effect of unit structural symmetry on the EOT characteristics of periodic subwavelength chiral and achiral hole arrays,which further reveals the dependence of the surface plasmon effects on the characteristics of the unit structural.The main works are listed as follows:(1)The EOT phenomenon of periodic subwavelength cross-shaped hole(non-chiral)arrays in metal films are numerically researched by 3D-FDTD method.The results show that the enhanced optical transmission characteristics of cross-shaped hole arrays in metal films is mainly influenced by SPs' effect which is excited on the surface of metallic films.The width and length of the cross-shaped have a great effect on the enhanced optical transmission of periodic subwavelength cross-shaped hole arrays by changing the LSP resonances.The symmetry of unit structural have dramaticly influences on the enhanced optical transmission of cross-shaped hole arrays.When the unit structure is asymmetric in the perpendicular to the polarization direction,the asymmetric LSP resonance will be formed in the perpendicular to the polarization direction of the unit hole,which will leads to the splitting of the transmission peak in the infrared wavelength.With parallel to the polarization direction of unit structure asymmetric,the asymmetric LSP resonance will be not formed in the parallel to the polarization direction,so it does not cause the splitting of the transmission peak in the infrared wavelength.(2)Based on the exploration the effect of symmetry on the enhanced light transmission of cross-shaped(non-chiral)hole arrays,3D-FDTD method is employed to study the enhanced optical transmission of periodic subwavelength broken gammadion-shaped(chiral)hole arrays.The results show that the symmetry of the unit structure has a great influence on the enhanced optical transmission of the broken gammadion-shaped hole array,and it has extremely difference with the influence of the symmetry of the unit structure on the enhanced optical transmission of the cross shaped hole array.For broken gammadion-shaped hole arrays,when the unit structure is symmetry broken in the perpendicular or parallel to polarization direction,the transmission peaks will split in infrared wavelength range and it is caused by the asymmetric LSP resonances.We also found that the thickness of metal film and periodic of arrays have effect on the enhanced optical transmission characteristics of subwavelength broken gammadion-shaped chiral hole arrays.