Talbot Effect Based On Surface Plasmon Polaritons And Its Super-diffraction Focusing Property

Talbot effect,as a lens-free imaging,is widely used in industrial applications such as spectrometers,lithography devices,positioning sensors,and refractive-index measurement instruments owing to its self-healing properties and peculiar imaging patterns.With the development of advanced nano-manufacturing technology,the research and analysis of Talbot effect has been extended to the plasma field.Therefore,the study of Talbot effect based on surface plasmon polaritons and its application is of great significance for device integration.The following are the main research work of this paper.1.The current status of domestic and international research on the Talbot effect and the current problems are summarized,and the significance of studying the Talbot effect of plasma polarization excitations is briefly discussed.Based on the angular spectrum theory and reciprocal lattice vector theory,the imaging principle of Talbot effect and the pattern of fractional Talbot imaging in one-dimensional grating and two-dimensional square arrays are analyzed.The Talbot effect of surface plasmon polaritons is demonstrated using dipole theory,and the distance formula for Talbot imaging in subwavelength structures is given.The finite-difference time-Domain method and the steps of modeling and simulation using FDTD Solutions are introduced in detail.2.A Talbot imaging scheme based on surface plasmon polaritons with periodic metal nanopore arrays is proposed,and its spatial tunability and self-healing ability are demonstrated by the FDTD method.The results reveal that the transverse field distribution at the Talbot planes can be offset in the 500nm range with the incident light angle changed from 0° to 25°,exhibiting a tunability of the spatial position.Meanwhile,the randomly missing and misaligned defects of such periodic metal nanopore arrays can be effectively restored by the presence of low density or defects located at the center.In addition,the principle of defect repair is discussed,and the conclusion that the perfect structures provide imaging information for defects is obtained.3.Based on the Talbot effect of surface plasmon polaritons,two kinds of metal nanostructures are proposed to realize super-diffraction focusing,which are periodic nanohole array and concentric ring.The influence of structural parameters on superdiffraction focusing characteristics is discussed and analyzed.The first structure is the periodic nanopore array structure with LiNbO3 as the filling medium inside the hole.It is proposed to achieve super-diffraction focusing by using the Talbot effect of surface plasmon polaritons.The full width at half maximum(FWHM)of the focused spot on the planes of 1/3ZT,1/2ZT and ZT less than one-third of the wavelength,and an imaging pattern similar to the classical fractional Talbot effect is found.In the concentric ring structure filled with medium in the ring,the effects of the radius of the central hole,the width of the ring and the number of rings on the focusing spot and the focusing intensity are analyzed.The concentric ring structure through the Au film is designed by selecting the optimal structural parameters.The focusing spot at the Talbot distance is less than half of the wavelength,and the depth of the focusing spot can be controlled by changing the number of rings.