Near Field and Far Field Optical Properties of Plasmonic Nano cylinders

Abstract

In this report we have studied the near field and the far field plasmonic prop- erties of gold nanocylinders arranged linearly in a Fibonacci number chain and compared the results with those arranged in a conventional geometry. Assigning the radius of first two nanocylinders as 10nm, we have arranged five gold nanocylinders linearly with radii varying according to Fibonacci numbers and compared the optical properties with conventional geometry. Using FEM simulation we explored the near field distribution and the far field radiation pattern of the two geometries for various excitation angles. Our study reveals significant backscattered intensity in the far field radia- tion pattern for excitation angles along the chain for Fibonacci geometry, which was otherwise absent in conventional geometry. A systematic varia- tion in near field enhancement is observed as a function of excitation angles which could guide us to tune Raman enhancement by changing the angle of excitation. We have obtained the maximum near field enhancement in the gap of two largest nanocylinders which is in contrast to the results obtained in the self similar chain of nanostructures. In addition we have explored the polarization dependent plasmonic properties of 1D silver nanowires and observed the strong dependence of incident polarization on propagation of surface plasmon polaritons.