Design of a Simple Integrated Coupler for SPP Excitation in a Dielectric Coated Ag Thin Film

A simple integrated coupler is proposed for the efficient excitation of surface plasmon polariton (SPP) mode in a thin metal film. The SPP mode is generated in a single Ag-dielectric interface by the incident field and coupled with an Ag thin film. The coupling efficiency at different wavelengths using two different dielectrics, gallium lanthanum sulfide (GLS) and aluminum gallium arsenide (AlGaAs) is calculated by analyzing the SPP propagation dynamics with the finite difference time domain method. A maximum coupling efficiency of 70% is obtained at a wavelength of 460 nm when GLS is used, whereas the corresponding value obtained for AlGaAs is 60% at 560 nm. The proposed structure can be used to excite SPPs in a nano-thin film from an external bulky source and is easier to fabricate since a single interface metal-dielectric configuration is used to excite the metal-thin film.