Dependence Of SPS Properties On Unit Structural Features Of Subwavelength Metal Hole Arrays

Plasmonics has attracted more and more attention in the field of both micro/nano photonics and integrated photonics since last decade, and its related research has always been the frontier and hot topic. Enhanced Optical Transmission(EOT) is one of the important research topics in plasmonics and it has attracted more and more researchers’ attention because of its underlying physical mechanism and widely potential applications.This thesis utilizes the finite-difference time-domain( FDTD)numerical calculation technique to explore the effects of unit structural features on EOT, and to study the physical mechanism of EOT phenomenon in periodic subwavelength Tai-Chi-shaped hole arrays. The main works are as follows:(1) Based on the thorough understanding of the basic concepts and properties of surface plasmons, the EOT phenomenon and its related researches’ status and trend are summarized. The basic theory of finite-difference time-domain method is derived in detail.(2) 3D finite-difference time-domain method is employed tocomparatively study the enhanced optical transmission of periodic subwavelength hole arrays in metallic silver films composed of circular-shaped, button-shaped, semicircular-shaped and Tai-Chi-shaped holes which have different symmetry deposited on a glass substrate. It turns out that EOT is strongly dependent on the symmetry of unit cell. With the reduction of unit structural symmetry, the transmission peak in infrared wavelengths range undergoes a large spectral red-shift, the spacing between the transmission peak in visible and infrared wavelengths range increases gradually, and the normalized transmission increases gradually. It is revealed that surface plasmon polaritons(SPPs) resonance mode due to the periodicity of hole arrays is the dominant factor to the optical transmission properties of these four arrays structures in visible wavelengths; SPPs mode dominates the optical transmission properties of the two hole arrays with good unit structural symmetry and localized surface plasmons(LSPs) mode of the subwavelength hole significantly affects the optical transmission properties of the two hole arrays with poor symmetry in infrared wavelengths.(3) 3D finite-difference time-domain method is employed to study the enhanced optical transmission of periodic subwavelength Tai-Chi-shaped holes arrays in silver films deposited on a quartz substrate. Results show the enhanced optical transmission properties of subwavelength Tai-Chi-shaped hole arrays in the visible and infrared wavelengths, and it is found that threeresonance modes occur in the transmission spectra due to the SPPs mode on the surface of Ag film, to the resonance effect of SPPs in the nanohole and to LSP resonance mode in the nanohole. By adjusting the polarization of incident light, film thickness, hole size and the periodicity of hole arrays, we observe the interesting phenomenon of spectral red shift, blue shift,strengthening, weakening and splitting in the transmission.