Properties Of The Surface Plamon Field Distribution Of The Metallic Grating/probe Hybridized Micro Structure

A surface plasmon polariton (SPP) is an electromagnetic excitation existing on the metal surface, which is based on electron's polarization. It is a TM surface electromagnetic wave, whose amplitude decays exponentially with increasing distance from the surface. Its electromagnetic field is confined to the near vicinity of the metal surface. The near field of SPP is very sensitive to the characteristic of the metallic structure's surface. Some nano-structures on the surface can significantly influence the whole field. Based on this property, we can manipulate the surface electromagnetic field and potential field by choosing particular metallic nano-structure. Furthermore, we can enhance the amplitude of near field based on surface plasmon enhancement and improve its manipulation function.Based on the properties above, we design a particular metallic hybridized micro structure with the characteristics of optical gratings and probe structures. By changing the parameters of nanostructures and the excitation, there will be particular potential field in the vicinity of metal surface. The potential field can be used in optical tweezers by applying the trapping function of near field.This paper starts from the fundamental physics of surface plasmon, and discusses its formation mechanism, existent condition and excitation method. We deduct the electromagnetic discretization difference recurrence equation for surface plasmon from the standpoint of Maxwell equations, and compute its surface field by using the method of FDTD on the programming platform of Matlab. By analyzing its surface potential field, we investigate that the potential well for trapping can be deep, when the central structure is designed like saw, and the other structures remain as optical gratings. The width of this potential well is about 2μm, which is close to some chemical molecule's diameter. The stable trapping field of optical tweezers created by this structure can manipulate some micro particles. The numerical simulation results will provide theoretical basis and guidance for the optical tweezers based on surface plasmon.