Simultaneous excitation of multi-spectral surface plasmon resonance using multi-stepped-thickness metallic film

Abstract

A new scheme of variable thickness ladder-like stepped metal film for simultaneous excitation of surface plasmon resonance (SPR) with different wavelength based on modified three layer Kretschmann configuration has been proposed. Metal thickness has been optimized for four different wavelengths ranging from visible to near infrared. The thickness has also been optimized for different substrates as well as different metal films in order to show the dependency of the substrate and metal layers on the ultimate performance of the plasmonic structure. A new concept of Reflectance Constrained Dynamic Range has been employed and its value has been calculated numerically and graphically for each SPR structure under consideration and for each wavelength considering water as reference sample and using the optimized metal thickness. Electric field enhancement has been evaluated for different structures and the full width half maximum has also been calculated for four working wavelengths in order to study the field confinement and measurement accuracy. Longer wavelength provides larger dynamic range and better measurement precision, which is desirable for biochemical sensing. Moreover, this multi-channel ladder-like stepped metallic structure can also be utilized for simultaneous sensing of different samples.