The Study Of Plasmonic Property Of A Pair Of Silver Nano-spheres Based On Gratings

When incident light illuminates a nano-sized metal structure, surface Plasmon polaritons can be generated on the surface of the metal. The research of this phenomenon grows further, which attracts scientists who study nanoscience. Surface Plasmon polaritons is a excited state generated when free electrons interact with incident electromagnetic wave under specific circumstance. In particular, it's an evanescent wave transmitting on the surface of metal. When the electromagnetic wave interact with free electrons, especially when the frequency of the oscillation of Plasmon equals the frequency of the electromagnetic wave, the Surface Plasmon polaritons are generated, which makes the electricity field increase intensively. Surface Plasmon polaritons are affected by the shape of the nanostructure, the size of the nanostructure, and the constituent of medium around. It makes the Surface Plasmon polaritons applied in near-field optics, nano-electronics, optoelectronics and so on. It also applied in nanooptics device, nano waveguide etc. In this paper, we use finite-difference time-domain method to study Plasmon resonance absorption characteristic of a pair of nano-silver spheres based on gratings.Firstly, we use FDTD simulate the electric field distribution when linear polarized monochromatic plane wave illuminate a pair of nano-silver spheres in vacuum. The result shows that for the pair of silver spheres whose radi are 40nm and the distance between them is lOnm, with the incident light whose wavelength is 300-1000nm, the resonance peak is unique, which is around 400nm. The electric field of the center of the space between the two spheres is local, which is two times stronger than other place.We set the former structure as control group, and study a pair of nano-silver spheres based on gratings illuminated by the same incident light as in control group. We observe the electric field of the center of the space between the two spheres, and electric field around the structure when illuminated by the incident light with a wavelength of 629.237nm. The result shows that, compared with the control group, this structure generates a stronger Surface Plasmon polaritons, which makes the electric field in the center of the space between the two spheres two times larger than the control group. Further research shows that this structure is sensitive to structure parameters, such as the width of the gratings, the height of the gratings, and so on.