Excitation and Optimization Modeling of Surface Plasmon Polaritons in a Concentric Circular Metallic Grating Film

Interaction behavior between surface plasmon polaritons (SPPs) and Hankel-distributed diffracted waves (DWs) on a silver concentric circular grating film is studied using a rigorous coupled-wave technique for circular structure. It is shown that the numerical technique reveals the excitation characteristics of SPPs in the circular metal grating as well as provides an accurate calculation of SPP intensities for further optimization designs. Results show that the SPPs can be excited by various DWs through the control of wavelength and angle of the incident light. The most efficient excitation of SPPs from this circular metal grating structure can be obtained from the +1st-order DW under a normal incidence with wavelength close to the grating period, and the optimal thickness and duty cycle of the grating are found to be 370 and 0.5 nm, respectively. It is shown that the optimized intensity of SPPs excited from circular metal grating can be higher than that from strip metal grating by over one order of magnitude.