Research On The Refractive Index Sensing Property Of Extraordinary Transmission Based On SPP’s Sub-wavelength Arrays

Surface Plasmon Polaritons(SPP)is a kind of special electromagnetic wave formed when the light irradiates the noble metal and excites the collective oscillation of free electrons on the surface.It conducts along the metal surface in the horizontal direction and exponentially decays perpendicular to the metal/ dielectric interface.It conducts along the metal surface in the horizontal direction and exponentially decays perpendicular to the metal/ insulator interface.SPP has a series of special physical characteristics such as near-field enhancement,sub-wavelength control,and surface localization.Due to the resonant coupling of the SPP,light has a strong transmission(EOT)phenomenon through the periodic subwavelength hole array structure.The EOT based transmission peak is very sensitive to the change of the refractive index of the surrounding environment.This feature provides a new method for designing high-performance refractive index sensors.In this paper,two kinds of sub-wavelength hole arrays with composite circular gold hole array and H-shaped gold hole array are designed theoretically.Then the finite-difference time-domain(FDTD)method was used to simulate the influence of the main structural parameters of the two devices on the EOT characteristics,and the parameters were optimized to obtain the best EOT characteristics.Finally,the refractive index sensing characteristics of the high performance SPP sensor are discussed under the optimal EOT characteristics.The main research works of this paper are as following:The metal circular arc hole array structure consisting of two symmetrical large and small circular arcs,at the positions of up and down,left and right is proposed.A good extraordinary optical transmission phenomenon will be obtained using a Fabry-Perot cavity formation by the structure to enhance surface plasmon polariton(SPP)coupling role.At the same time,a refractive index sensing property is investigated based on the phenomenon.The effects of the radius of big,small circular arc hole array,the center distance of two circular arcs hole and the array period on extraordinary optical transmission phenomenon are investigated by using the finite-difference time-domain(FDTD)method.It is found that the radius of the big,small two circular arcs being 95 nm and 70 nm,respectively,the center distance of the two circular arcs being 100 nm and the period being 425 nm in this structure,it has an extraordinary optical transmission phenomenon.Then,the refractive index sensing property is discussed based on the phenomenon whose sensitivity is 279 nm/RIU.These results serve as a theory reference for the design of next generation high performance micro-nano plasmonics sensors.A H-shaped metal hole arrays structure was proposed,then it was used to form the Fabry-Perot cavity to enhance the surface plasmon polarizations(SPP)coupling effect,hoping to obtain a better optical transmission phenomenon.H-shaped hole arrays consists of a vertical rectangular hole and a horizontal two symmetrical rectangular holes,thus the effects of parameters of the holes,such as the length and the width,on the transmission characteristics were studied in detail by using the finite-difference time-domain(FDTD)method.Meanwhile,the refractive index sensing property was investigated based on the phenomenon.It is found that when the length and the width of the vertical rectangle holes are 300 nm and 120 nm,and he length of the two symmetric rectangular holes in the horizontal direction are 60 nm and 10 nm respectively,a strong transmission phenomenon can be realzied.And the sensitivity of the refractive index can reach 389 RIU/nm.An experimental scheme for preparing a subwavelength gold hole array sensor device using a silicon template transfer method is initially proposed,so that the template can be used,thereby effectively reducing costs and shortening the nano processing time.