Bimetallic silver-gold film waveguide surface plasmon resonance sensor

Abstract

A waveguide surface plasmon resonance (SPR) optical sensor based on wavelength modulation is presented. Strip waveguides are fabricated using MicroChem's SU-8 photoresist via UV lithography. Next, a bimetallic silver-gold film is deposited on the waveguides for exciting surface plasmon resonance. The underlying silver yields better evanescent field enhancement of the sensing surface, while the overlying gold ensures that the stability of the metallic film is not compromised. Experiments were conducted using various glucose concentrations as the analyte, and the normalized transmission output of the waveguide shows a good SPR curve for all the analytes. With a better evanescent field extension, the proposed waveguide SPR configuration extends the use of SPR, especially in bio-sensing, as longer ligands can be immobilized and bigger analytes can be monitored.